Effects of Anthropogenic Disturbance of Natural Habitats on the Feeding Ecology of Moorish Geckos

Abstract

Urbanization and anthropic influences can drastically modify a natural habitat and transform it into an easily recognizable “urban habitat”. Human activities can also induce less severe modifications of what apparently might still look like natural habitats. Therefore, these subtle alterations may be hidden but can still cause important negative effects on plant and animals. In contrast, some species seem able to take advantage of these anthropic alterations. Here, we examined the possible effects of the anthropogenic disturbance of an apparent natural habitat on the feeding ecology and body condition of Moorish geckos, Tarentola mauritanica. For this, we compared microhabitat structure, invertebrate availability, the diet composition (estimated from fecal contents), diet selection patterns and body condition of the two populations of geckos inhabiting two contiguous small islands. These islands have similar environmental characteristics, but highly contrasting differences in urbanization and anthropogenic influence. We found that, although the abundance of potential invertebrate prey was similar on both habitats, the diversity of invertebrate prey was lower in the altered habitat. As a consequence, although composition of the diet of geckos was similar on both islands, the diversity of prey and food niche breadth were lower in the altered habitat, and patterns of diet selection changed. However, these inter-habitat differences did not seem to affect the body size and body condition of geckos. We discuss how flexibility in feeding ecology may allow some species to cope with small anthropic disturbances of the habitat.

Full text

Citation: Martín, J.; Ortega, J.;
García-Roa, R.; Rodríguez-Ruiz, G.;
Pérez-Cembranos, A.; Pérez-Mellado,
V. Effects of Anthropogenic
Disturbance of Natural Habitats on
the Feeding Ecology of Moorish
Geckos. Animals 2023,13, 1413.
https://doi.org/10.3390/
ani13081413
Academic Editor: Fernando
Martínez-Freiría
Received: 18 March 2023
Revised: 15 April 2023
Accepted: 18 April 2023
Published: 20 April 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
animals
Article
Effects of Anthropogenic Disturbance of Natural Habitats on
the Feeding Ecology of Moorish Geckos
JoséMartín1, * , Jesús Ortega 1,2, Roberto García-Roa 1,2, Gonzalo Rodríguez-Ruiz 1, Ana Pérez-Cembranos 3
and Valentín Pérez-Mellado 3
1Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, C/JoséGutiérrez
Abascal 2, 28006 Madrid, Spain
2Ethology Lab, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia,
46980 Valencia, Spain
3Departamento de Biología Animal, Universidad de Salamanca, 37007 Salamanca, Spain
*Correspondence: jose.martin@mncn.csic.es
Simple Summary:
Humans can alter the habitat quality and negatively affect many animals. How-
ever, some species seem able to cope with or even take advantage of these alterations. This study
examines the effects of small anthropogenic alterations of a natural habitat on the feeding ecology of
a gecko, Tarentola mauritanica. We compared geckos found in two contiguous small islands with either
natural or human-altered seminatural habitats. Results showed that seminatural habitats differed
from actual natural habitats in some microhabitat characteristics and in diversity of available prey.
The diet of geckos also differed between habitats, being less diverse in altered habitats. However,
the health state (body condition) of geckos was similar between habitats. These geckos seem able to
modify their diet selection patterns to cope with anthropic disturbances of the habitat, which would
allow them to inhabit and prosper in human-altered ecosystems.
Abstract:
Urbanization and anthropic influences can drastically modify a natural habitat and trans-
form it into an easily recognizable “urban habitat”. Human activities can also induce less severe
modifications of what apparently might still look like natural habitats. Therefore, these subtle alter-
ations may be hidden but can still cause important negative effects on plant and animals. In contrast,
some species seem able to take advantage of these anthropic alterations. Here, we examined the
possible effects of the anthropogenic disturbance of an apparent natural habitat on the feeding ecology
and body condition of Moorish geckos, Tarentola mauritanica. For this, we compared microhabitat
structure, invertebrate availability, the diet composition (estimated from fecal contents), diet selection
patterns and body condition of the two populations of geckos inhabiting two contiguous small
islands. These islands have similar environmental characteristics, but highly contrasting differences
in urbanization and anthropogenic influence. We found that, although the abundance of potential
invertebrate prey was similar on both habitats, the diversity of invertebrate prey was lower in the
altered habitat. As a consequence, although composition of the diet of geckos was similar on both
islands, the diversity of prey and food niche breadth were lower in the altered habitat, and patterns
of diet selection changed. However, these inter-habitat differences did not seem to affect the body
size and body condition of geckos. We discuss how flexibility in feeding ecology may allow some
species to cope with small anthropic disturbances of the habitat.
Keywords:
diet selection; feeding ecology; gecko; human disturbance; invertebrate prey; reptiles;
Tarentola
1. Introduction
Urbanization and other anthropic influences can cause severe drastic disturbances
to the environment, transforming a natural habitat into an “urban habitat”, with peculiar
Animals 2023,13, 1413. https://doi.org/10.3390/ani13081413 https://www.mdpi.com/journal/animals

Animals 2023,13, 1413 2 of 14
and conspicuous differences that are immediately recognizable [
1
–
3
]. Human activities can
also induce less severe, at times even subtle, modifications of a habitat that do not result in
conspicuous changes in the “visual appearance” of that habitat. Consequently, these altered
semi-natural habitats might still be mistaken for genuine natural ones, at least without
doing detailed examinations of their state [
4
]. However, even some apparently minor and
inconspicuous anthropogenic alteration of a habitat may be a threat to animals [2].
Although anthropic habitat alterations may cause the decline of many species [
5
],
other species seem able to take advantage of the new resources and opportunities derived
from anthropogenic disturbance, being even more abundant in human-altered habitats.
For example, some species of lizards and geckos can be even more abundant in urban
areas outside of their natural range [
6
,
7
]. The adaptation of animals to anthropic habitats is
possible due to phenotypic changes derived from genomic adaptation after natural selec-
tion [
8
,
9
]. However, animals may also show behavioral flexibility [
10
,
11
] in, for example,
microhabitat use and movements [
12
], habituation to inefficient human “predators” [
13
],
or diet composition [
14
–
16
]. This behavioral plasticity might be especially important when
animals inhabiting a natural habitat start to experience the effects of anthropic disturbances.
Therefore, it is interesting to examine whether and how species that occupy habitats with
different levels of anthropic influence can cope with habitat alterations and show behav-
ioral flexibility.
The Moorish gecko, Tarentola mauritanica, is a Mediterranean species associated with
rocky areas, where it can move easily thanks to the adhesive strips on its fingers [
17
]. In
natural habitats, this gecko selects large rocks or groups of small rocks behind which to
inhabit [
18
]. However, other populations of this gecko are anthropophilic, being found in
human constructions (walls separating farms, buildings, cisterns, etc.) even inside cities,
provided that there are shelters for them to hide behind [
17
,
19
]. The diet of T. mauritanica
has been examined in different populations, as can be seen in review [
17
], showing that
it is a generalist species that feeds mainly on ground-dwelling arthropods and other
invertebrates, e.g., [
19
–
23
], but that its diet also includes some flying insects, especially
inside urban areas [
24
]. However, it is not well known whether, in natural habitats that
have suffered some anthropic disturbance, the expected effects on prey availability affect
the diet composition of T. mauritanica. Moreover, it is not known whether this gecko is able
to modify its diet selection patterns to respond to the presumed changes in available prey.
Further, it is not known whether changes in diet derived from habitat alterations might
directly affect the health state of geckos.
Here, we examined the possible effects of anthropogenic disturbances to and mod-
ifications of a natural habitat, which still might look natural in comparison with a truly
unaltered natural habitat, on the feeding ecology of T. mauritanica geckos. For this, we
compared two contiguous small islands with similar environmental characteristics (climate,
vegetation, topography, etc.), but highly contrasting differences in urbanization and anthro-
pogenic influence (actual unaltered natural habitats vs. apparently natural habitats with
anthropic disturbances; see methods). In each island, we estimated the habitat structure,
the availability of invertebrates in the habitat, the diet composition (based on fecal con-
tents), diet selection patterns and body size and condition of geckos. We expect that the
anthropogenic influence on the natural habitats should modify the habitat characteristics,
which would affect the abundance or types of available prey and, therefore, the diet of
geckos. We also expect that these modifications might have consequences on the body
condition of geckos. However, geckos might be able to use flexibility to modify their diet
selection patterns to cope with these human-induced changes.
2. Materials and Methods
2.1. Study Area
We performed the field work in the spring (March) of 2015 at the Chafarinas archipelago
(Spain) (35
◦
11
0
N, 02
◦
25
0
W) (Figure 1a). These islands are located off the North African Mo-
roccan coast in the western Mediterranean Sea, close to the shore, and are strictly protected

Animals 2023,13, 1413 3 of 14
as a nature reserve. The climate is a Mediterranean semiarid (dry and warm), the natural
vegetation consists of woody bushes (Genus Suaeda,Salsola and Lycium) and there are
abundant rocky areas where T. mauritanica geckos take refuge (Figure 1b). There are three
islands, but abundant populations of T. mauritanica are found on only two of the islands
(‘Isabel’ and ‘Rey’) [
25
]. One of the islands (‘Rey’; 13.9 ha) has been never been inhabited by
humans and maintains highly restricted access to visitors (limited to occasional short visits
by a few wardens and researchers); thus, this island maintains natural pristine conditions.
Another island (‘Isabel’; 15.1 ha) has been inhabited by humans since ancient historical eras
times. Nowadays, only a small human population (around 50 people) live there, but the
island supported up to 5000 people at the beginning of the 20th century. Nearly 60% of its
surface is covered with buildings or paved streets. However, close to and scattered between
buildings, there are remains of seminatural vegetated areas. These areas are apparently
similar to those found in the naturally preserved Rey Island, but they have been highly
modified, as shown by the evidence of anthropogenic influence in some areas (soil erosion,
organic and artificial residues, pathways marked with whitewashed rocks, presence of
ornamental trees and bushes, etc.). Geckos are abundant in rocky areas in the natural areas;
conversely, in seminatural areas, geckos are also abundant not only under rocks but also
below anthropogenic materials, such as bricks or tiles. The third island (‘Congreso’) only
holds several introduced individual geckos, which are restricted to a single uninhabited
small concrete cabin used as a material store.
Animals 2023, 13, x 3 of 14
2. Materials and Methods
2.1. Study Area
We performed the field work in the spring (March) of 2015 at the Chafarinas archi-
pelago (Spain) (35°11′ N, 02°25′ W) (Figure 1a). These islands are located off the North
African Moroccan coast in the western Mediterranean Sea, close to the shore, and are
strictly protected as a nature reserve. The climate is a Mediterranean semiarid (dry and
warm), the natural vegetation consists of woody bushes (Genus Suaeda, Salsola and
Lycium) and there are abundant rocky areas where T. mauritanica geckos take refuge (Fig-
ure 1b). There are three islands, but abundant populations of T. mauritanica are found on
only two of the islands (‘Isabel’ and ‘Rey’) [25]. One of the islands (‘Rey’; 13.9 ha) has been
never been inhabited by humans and maintains highly restricted access to visitors (limited
to occasional short visits by a few wardens and researchers); thus, this island maintains
natural pristine conditions. Another island (‘Isabel’; 15.1 ha) has been inhabited by hu-
mans since ancient historical eras times. Nowadays, only a small human population
(around 50 people) live there, but the island supported up to 5000 people at the beginning
of the 20th century. Nearly 60% of its surface is covered with buildings or paved streets.
However, close to and scattered between buildings, there are remains of seminatural veg-
etated areas. These areas are apparently similar to those found in the naturally preserved
Rey Island, but they have been highly modified, as shown by the evidence of anthropo-
genic influence in some areas (soil erosion, organic and artificial residues, pathways
marked with whitewashed rocks, presence of ornamental trees and bushes, etc.). Geckos
are abundant in rocky areas in the natural areas; conversely, in seminatural areas, geckos
are also abundant not only under rocks but also below anthropogenic materials, such as
bricks or tiles. The third island (‘Congreso’) only holds several introduced individual
geckos, which are restricted to a single uninhabited small concrete cabin used as a material
store.
Figure 1. (a) Typical natural habitat at the Chafarinas Islands, with the uninhabited Rey Island in
the foreground; the human-inhabited Isabel Island behind it in the middle, showing an apparently
similar, but altered, seminatural habitat scattered between the buildings; and the Congreso Island
in the background; (b) an adult T. mauritanica gecko on a rock in its natural habitat.
(a)
(b)
Figure 1.
(
a
) Typical natural habitat at the Chafarinas Islands, with the uninhabited Rey Island in
the foreground; the human-inhabited Isabel Island behind it in the middle, showing an apparently
similar, but altered, seminatural habitat scattered between the buildings; and the Congreso Island in
the background; (b) an adult T. mauritanica gecko on a rock in its natural habitat.
2.2. Effects of Human Disturbance on Microhabitat Characteristics
To characterize the microhabitats where we found T. mauritanica geckos on the two
study islands (Isabel and Rey), we made a series of random transects covering all the
available natural (on Rey Island) and seminatural (on Isabel island) habitats (i.e., excluding
paved areas and buildings). Every 25 m, we chose the nearest rock to the transect point
that might hold geckos (i.e., >10 cm length) as the center of a circular sampling area of
2 m diameter around the rock. In this area, we visually estimated percentage cover at the
ground level of ‘bare-soil’ with gravel, ‘rocks’ (>10 cm) and ‘grasses’, and, above surface

Animals 2023,13, 1413 4 of 14
level, the cover of the dominant large woody ‘bushes’ and ‘mean bush height’ (Table 1).
For similar methods, see [
26
]. One expected effect of human disturbance is an increase
in soil compaction due to erosion and trampling, which might affect the abundance of
soil invertebrates [
2
]. Hence, we measured ‘soil compaction’ with a hand penetrometer
(Eijkelkamp Co., Em Giesbeek, The Netherlands) that we pushed slowly and vertically into
the soil [
27
]. For each sampling point, we took and calculated the mean of five random
measures of compaction from the area surrounding the sampling rock.
Table 1.
Characteristics of microhabitats (mean
±
SE) at two of the Chafarinas Islands with different
levels of anthropogenic disturbance (natural: Rey; altered: Isabel) based on 54 random habitat
samples. The statistics (Fand p) are given from one-way ANOVAs tests comparing both islands.
Significant comparisons are marked in bold.
Rey Island
(Natural)
(n= 29 Points)
Isabel Island
(Altered)
(n= 25 Points)
Mean ±SE Mean ±SE F1,52 p
Bare soil with gravel (%) 55.0 ±4.8 42.8 ±4.2 3.52 0.066
Rocks (%) 27.1 ±3.8 23.8 ±3.1 0.43 0.52
Grasses (%) 17.9 ±3.4 33.4 ±4.5 7.89 0.007
Bushes (%) 27.2 ±4.5 15.0 ±2.4 5.21 0.027
Mean bush height (cm) 52 ±9 74 ±12 2.30 0.13
Soil compaction (kg cm−2)1.11 ±0.13 1.71 ±0.19 6.84 0.011
2.3. Availability of Potential Prey
We estimated the availability in the environment of invertebrates that could be poten-
tial prey of T. mauritanica geckos. In the same areas and microhabitats where we captured
geckos, we randomly lifted rocks behind which geckos might take refuge (i.e., >10 cm
length). Then, we counted the invertebrates (>2 mm long) for two minutes, identified to
order or family level, that were found on the substrate below and on the undersurface of the
turned rock, and in the50 cm radius around the rock. During the survey time, we counted
invertebrates that were in this area or those which had escaped (e.g., isopods, centipedes
or spiders), and also those that came flying and landed (flies, butterflies, etc.) (for similar
procedures, see [
28
–
30
]). We also used a small stick to excavate the soil and leaf litter in
the sampling area, looking for invertebrates buried close to the surface, such as insect
larvae. With this standardized recording method, we estimated the relative abundance of
the different types of invertebrates that were actually available in the gecko microhabitats.
2.4. Geckos Sampling Procedures
We conducted daily surveys to cover all the available natural and seminatural habitats
on the two study islands (Isabel and Rey). We searched for T. mauritanica geckos by lifting
rocks that active geckos used as refuges. To obtain diet samples, we collected the feces
of live geckos captured by hand. We gently compressed the vents of geckos to force the
expulsion of feces, and, sometimes, we had to place geckos in a plastic cage and wait
some minutes until they voluntary expulsed the feces. Feces were stored individually in
labeled Eppendorf vials. Sexes of adult individuals were identified by pressing gently
around the cloacae to try the partial eversion of hemipenis of males. Juveniles could not be
reliably sexed.
We used a metallic ruler to measure (to the nearest 1 mm) the ‘snout-to-vent length’ of
geckos (SVL; i.e., the distance from the snout
'
s tip to the posterior extreme of the cloacal
scales) and ‘tail length’ and noted if the tail was original or regenerated. We measured
‘body mass’ with an electronic digital balance (0.1 g of precision). We calculated a ‘body
condition index’ (BCI) using the residuals of the leastsquares linear regression between
mass and total length (both log
10
-transformed) (r= 0.72, F
1,115
= 126.95, p< 0.001). These
residuals measure the condition of an animal independently of its body size [
31
,
32
]. We

Animals 2023,13, 1413 5 of 14
also calculated, as an alternative to the BCI, the ‘scaled mass index’ (SMI) [
33
] by following
the formula: SMI = Wi [L
0
/L
i
]
bSMA
, where W
i
is the body mass and L
i
the SVL of a given
individual, L
0
is the average SVL of all individuals, included as a standardized value to
which compare each individual value, and bSMA is the slope of a standardized major axis
regression. Body condition indices have been considered to constitute a way of estimating
the health state of many animals, including reptiles [34,35].
To avoid sampling the same individuals twice, we did not sample the same areas
twice. Geckos were released in good health a few minutes later at the exact point where
they had been found.
2.5. Analyses of Fecal Contents of Geckos
We used a binocular microscope to identify to order or family level the prey remains
present in fecal pellets. The analysis of fecal pellets is a useful non-invasive method
to examine diet while avoiding damage to animals [
28
,
36
–
39
]. Only easily identified
remains were used to conservatively estimate the numbers of each prey type per fecal
pellet. To minimize missing soft-body prey that might have been destroyed by the digestive
process [
40
], we carefully searched for the body parts of soft-body prey that were less likely
to be digested (e.g., head capsules of insect larvae, chelicerae and cephalic region of spiders).
In lizards, diet composition based on the visual analysis of fecal pellet contents is highly
comparable to diet analyses based on gastric contents of killed animals [
41
], and results
are even very close to those obtained for the molecular analyses (DNA metabarcoding) of
invertebrate prey presence in fecal pellets [42].
2.6. Data Analyses
The availability in the habitat in each of the two islands of each class of invertebrate
was characterized using the ‘abundance’ (total number) and ‘presence’ (percentage of
sampling points where a particular type of invertebrate was found) values. Similarly, the
diet of geckos was described using the ‘prey abundance’ (percentage of a given prey type
in relation to the total number of prey) and the ‘prey presence’ (percentage of individual
geckos that had consumed a given prey type) measures. Diversity of invertebrates in the
habitat and in the diet were calculated using the Shannon–Weaver ’s index, [
43
]: H
0
=
−Σ
p
i
ln p
i
, for the proportion (p
i
) of each of the taxonomic categories identified. To compare
H
0
indices between islands, we used Hutcheson’s ttest [
44
]. We also estimated the food
niche breadth (B) of geckos using the inverse of Simpson’s diversity, index [
45
]: B = 1/
Σ
p
i2
,
where p
i
is the proportion of prey resource i. This Bindex value was also calculated after
standardizing it by dividing Bby the number of actually used prey categories. To estimate
the overlap in diet composition of geckos between islands, we used the symmetric index of
Pianka [
45
]: O
jk
=(
Σ
p
ij
p
ik
)/
√
(
Σ
p
ij2
)(
Σ
p
ik2
), where p
ij
is the relative occurrence of prey type
iin the diet on the island jand p
ik
is the relative occurrence of prey type iin the diet on the
island k. This index ranges from 0 to 1, with 1 indicating complete overlap.
The relationships between availability and diet within and between islands were first
compared using Spearman’s rank correlations and
χ2
tests. Then, in order to estimate
selection for a prey type, we used the selectivity index (D) of Ivlev [
46
], modified by
Jacobs [
47
], following the formula: D = (r
−
p)/(r + p
−
2rp), where ris the proportion
of a given prey type in geckos
'
diet and pis the proportion of that prey available in the
environment. We selected this index because it is widely used in most studies of feeding
preferences. However, the error in Dmay be high when there are low sample numbers in
some prey categories [
48
]. To solve this problem, we calculated the relativized electivity
index (E*) of Vanderploeg and Scavia [
49
]. This index is a measure of the feeder’s perception
of a prey’s value, considering both its abundance and the abundance of other available prey
types. The E* index follows the formula: E*
i
=[W
i−
(1/n)]/[W
i
+(1/n)], which includes
the number of prey types available (n) and the selectivity coefficient W
i
=(r
i
/p
i
)/
Σ
i(r
i
/p
i
),
which uses the proportions of prey iin the diet (r
i
) and in the environment (p
i
). These two
selectivity indices range from
−
1 (total avoidance) through 0 (no or random selection) to

Animals 2023,13, 1413 6 of 14
+1 (maximum positive selection). We used
χ2
tests to test for the significance of electivities,
comparing the observed proportions of each prey type in feces, with expected values being
the proportions of prey available in the habitat (restricted to the types of prey actually
consumed by geckos) [50].
3. Results
3.1. Effects of Human Disturbance on Microhabitat Characteristics
In spite of the fact that the visual “appearance” of the natural habitat might look
similar on both islands, there were some significant differences between islands that could
be related to the level of anthropogenic disturbance. Thus, on the island inhabited by
humans (Isabel), there was a significantly lower coverage by bushes, but a significantly
higher cover of grass, while the height of the bushes and the cover of bare soil and rocks
did not significantly differ between islands. Additionally, soil compaction was significantly
higher on the island with anthropogenic influence (Table 1). Moreover, considering only
the data from Isabel Island, 56% of the seminatural sites sampled showed some signs of
direct human disturbance, such as the presence of artificial residues (e.g., bricks, ceramics,
glass, metals or plastic), whitewashed rocks, etc.
3.2. Availability of Potential Invertebrate Prey
We estimated the availability of invertebrates at 193 points, of which most sites (94.8%)
contained some invertebrates larger than 2 mm (Table 2). Nevertheless, significantly more
sites were empty of potential prey on Rey than on Isabel (8.1% vs. 1.2%;
χ2
= 4.56,
p= 0.033).
Considering the rank-order importance of the different types of invertebrates, availability
was similar on both islands (Spearman’s correlation, r
s
= 0.83, n= 18,
t= 5.96,
p< 0.0001).
However, there were some differences in the relative proportions of the different types of
invertebrates (
χ2
= 57.79, df = 17, p< 0.0001) (Table 2). While on Rey the three most abundant
invertebrate types were, in order of abundance, Formicidae (ants), Isopoda (isopods) and
Coleoptera (beetles) (these three groups accounting for 69.1% of all invertebrates), on Isabel
the most abundant types were Gastropoda (snails), Isopoda and Formicidae (76.1% of
all invertebrates). The invertebrates most frequently found in the habitat on Rey were
Gastropoda, Coleoptera and Isopoda, and, similarly but in a different order, on Isabel were
Isopoda, Gastropoda and Coleoptera. The total number of available invertebrates was
similar on both islands (one-way ANOVA, log-transformed data,
F1,191 = 0.13,
p= 0.71), but
the diversity of invertebrate types was significantly higher on Rey (H
'±
s
2H
= 1.93
±
0.01)
than on Isabel (1.80 ±0.01) (Hutcheson’s ttest, t= 2.53, df = 1670, p= 0.011).
Table 2.
Total abundance of invertebrates (>2 mm) available at two of the Chafarinas Islands with
different levels of anthropogenic disturbance (natural: Rey; altered: Isabel) based on 193 random
habitat samples. ‘Abundance’ (total number, % and mean number
±
SE of organisms at each sampling
point) and ‘Presence’ (proportion of sites containing a particular organism) are given.
Rey Island
(Natural)
n= 111 Points
Isabel Island
(Altered)
n= 82 Points
Abundance Presence Abundance Presence
n% Mean ±SE % n% Mean ±SE %
Gastropoda 112 9.9 1.01 ±0.15 37.8 172 21.9 2.10±0.36 63.4
Pseudoscorpion
4 0.3 0.04 ±0.02 8.0 6 0.8 0.07 ±0.05 3.7
Araneae 36 3.2 0.32 ±0.07 23.4 18 2.3 0.22 ±0.06 18.3
Opiliones 2 0.2 0.02 ±0.01 1.8 1 0.1 0.01 ±0.01 1.2
Acarina 3 0.3 0.03 ±0.03 0.9 13 1.6 0.16 ±0.07 8.5
Isopoda 198 17.5 1.78 ±0.44 31.5 283 36.0 3.45 ±0.59 54.9
Chilopoda 41 3.6 0.37 ±0.08 23.4 15 1.9 0.18 ±0.07 9.8
Thysanura 84 7.4 0.76 ±0.19 25.2 26 3.3 0.32 ±0.15 12.2

Animals 2023,13, 1413 7 of 14
Table 2. Cont.
Rey Island
(Natural)
n= 111 Points
Isabel Island
(Altered)
n= 82 Points
Abundance Presence Abundance Presence
n% Mean ±SE % n% Mean ±SE %
Dictyoptera 5 0.4 0.02 ±0.01 3.6 3 0.4 0.04 ±0.02 3.7
Embioptera 27 2.4 0.02 ±0.01 5.4 1 0.1 0.01 ±0.01 1.2
Homoptera 2 0.2 0.02 ±0.01 1.8 1 0.1 0.01 ±0.01 1.2
Heteroptera 11 1.0 0.10 ±0.08 2.7 3 0.4 0.04 ±0.03 2.4
Diptera 11 1.0 0.10 ±0.03 9.9 6 0.8 0.07 ±0.04 4.9
Lepidoptera 3 0.3 0.03 ±0.02 2.7 2 0.3 0.02 ±0.02 2.4
Coleoptera 173 15.3 1.56 ±0.46 25.9 85 10.8 1.04 ±0.17 48.8
Hymenoptera 2 0.2 0.02 ±0.01 1.8 2 0.2 0.02 ±0.02 2.4
Formicidae 409 36.3 3.68 ±9.91 22.5 144 18.3 1.76 ±0.56 39.0
Insect larvae 5 0.4 0.05 ±0.02 3.6 6 0.8 0.07 ±0.03 7.9
Total Invertebr. 1128 100 10.16 ±1.08 91.9 787 100 9.60 ±1.02 98.8
3.3. Diet of the Geckos
We obtained a total of 117 fecal samples from T. mauritanica geckos (Table 3). The num-
ber of individual prey items that could be identified per fecal pellet ranged between 1 and
12 and was similar across islands (One-way ANOVA, log-transformed data,
F1,115 = 0.79,
p= 0.38) (Table 3). The composition of the diet of geckos was similar in rank order of
importance between islands (Spearman’s correlation, r
s
= 0.78, n= 15, t= 5.22, p< 0.0001)
and there was a high niche overlap between islands (O= 0.94). On both islands, the diet
consisted mainly of Coleoptera, followed by Araneae and insect larvae, these being the
most abundant and frequent prey types (these three types accounting for an overall 76% of
prey), and other invertebrates were found in lower proportions (Table 3). However, there
were some differences between islands in the relative contribution of the different prey
types to the diet (
χ2
= 37.29, df = 15, p< 0.005), and more different prey categories were
consumed on Isabel (n= 15) than on Rey (n= 11). Moreover, the diversity of invertebrate
types was significantly higher in the diet of geckos from Rey (H
'±
s
2H
= 1.91
±
0.01) than
in geckos from Isabel (1.48
±
0.01) (Hutcheson’s ttest, t= 2.98, df = 229, p= 0.003). Similarly,
food niche breadth of geckos was higher on Rey (B= 4.75; standardized B= 0.34) than on
Isabel (B= 2.52; standardized B= 0.11).
3.4. Diet Selection Patterns
Overall, the diet of T. mauritanica geckos did not reflect the availability of invertebrates
in the habitat (Spearman’s correlation, Rey: r
s
= -0.01, n= 18, t=
−
0.02, p= 0.99; Isabel:
rs= 0.18,
n= 18, t= 0.73, p= 0.47). Particularly, we may anecdotally state that some inverte-
brate types such as Gastropoda, Isopoda and Formicidae were not consumed in spite of
being the most abundant invertebrates available in the habitat (Table 4). Neither Chilopoda,
Thysanura nor Embiotera were consumed by geckos. Instead, geckos selected positively
less abundant prey such as insect larvae or Dyctioptera. Additionally, Coleoptera and
Araneae were selected on Isabel Island, where these varieties of prey were less abundant;
conversely, on Rey, the higher availability of Coleoptera and Araneae seemed to fulfill
the dietary requirements of geckos. Thus, they did not require a positive selection. Other
invertebrates that were relatively scarce in the habitat, such as Lepidoptera, were also
positively selected, while other minor types of prey were consumed in proportions similar
to the expected by their availability in the habitat.

Animals 2023,13, 1413 8 of 14
Table 3.
Composition of the diet of the Moorish gecko, Tarentola mauritanica, in two of the Chafarinas
Islands with different levels of anthropogenic disturbance (natural: Rey; altered: Isabel), based on
117 fecal samples collected from live geckos. ‘Abundance’ (total number, % and mean number
±
SE
of prey in each fecal sample) and ‘Presence’ (percentage of fecal samples containing a particular prey
item) are shown.
Rey Island
(Natural)
n= 39 Fecal Pellets
Isabel Island
(Altered)
n= 78 Fecal Pellets
Abundance Presence Abundance Presence
n% Mean ±SE % n% Mean ±SE %
Gastropoda 3 1.5 0.04 ±0.02 3.8
Pseudoscorpion 3 3.5 0.08 ±0.04 7.7 2 1.0 0.03 ±0.02 2.6
Araneae 11 12.8 0.28 ±0.07 28.2 23 11.7 0.29 ±0.06 26.9
Opiliones 1 0.5 0.01 ±0.01 1.3
Isopoda 2 2.3 0.06 ±0.04 5.1 1 0.5 0.01 ±0.01 1.3
Dictyoptera 9 10.5 0.23 ±0.09 17.9 6 3.0 0.08 ±0.03 7.7
Homoptera 2 2.3 0.05 ±0.04 5.1 1 0.5 0.01 ±0.01 1.3
Heteroptera 2 2.3 0.05 ±0.04 5.1 1 0.5 0.01 ±0.01 1.3
Diptera 4 4.5 0.10 ±0.05 10.3 5 2.5 0.06 ±0.03 6.4
Lepidoptera 9 10.5 0.23 ±0.07 23.1 5 2.5 0.06 ±0.03 6.4
Coleoptera 34 39.5 0.87 ±0.18 51.3 120 60.9 1.56 ±0.25 60.3
Hymenoptera 1 0.5 0.01 ±0.01 1.3
Formicidae 2 1.0 0.03 ±0.02 2.6
Insect larvae 9 10.5 0.23 ±0.07 23.1 18 9.1 0.23 ±0.06 21.8
Arthropoda indet. 1 1.2 0.03 ±0.03 2.6 8 4.1 0.10 ±0.04 10.3
Total prey 86 100 2.21 ±0.20 100 197 100 2.53 ±0.25 100
Table 4.
Prey selection by the Moorish gecko, Tarentola mauritanica, in two of the Chafarinas Islands
with different levels of anthropogenic disturbance (natural: Rey; altered: Isabel). The electivity index
of Jacobs (D) and the Vanderploeg and Scavia’s relativized electivity index (E*) are given for each
potential prey type. The statistical significance (pfrom a
χ2
test) of this E* index is given. Significant
electivities are marked in bold.
Rey Island
(Natural)
Isabel Island
(Altered)
Electivity Index Electivity Index
D E* p D E* p
Gastropoda −1−1−0.895 −0.957 <0.0001
Pseudoscorpion +0.821 +0.514 0.058 +0.143 −0.407 0.79
Araneae +0.633 +0.119 0.20 +0.699 +0.236 <0.0001
Opiliones −1−1 +0.601 +0.117 0.32
Acarina −1−1−1−1
Isopoda −0.799 −0.919 <0.0001 −0.982 −0.991 <0.0001
Chilopoda −1−1−1−1
Thysanura −1−1−1−1
Dictyoptera +0.927 +0.764 <0.0001 +0.783 +0.434 0.001
Embioptera −1−1−1−1
Homoptera +0.861 +0.612 0.068 +0.601 +0.117 0.32
Heteroptera +0.416 −0.139 0.34 +0.143 −0.407 0.86
Diptera +0.664 +0.203 0.28 +0.544 +0.027 0.052
Lepidoptera +0.956 +0.851 <0.0001 +0.822 +0.520 0.0013
Coleoptera +0.566 −0.101 0.91 +0.859 +0.282 <0.0001
Hymenoptera −1−1 +0.334 −0.225 0.61
Formicidae −1−1−0.912 −0.965 <0.0001
Insect larvae +0.927 +0.764 <0.0001 +0.858 +0.583 <0.0001

Animals 2023,13, 1413 9 of 14
The diversity of invertebrates available in the habitat on Isabel was significantly higher
than the diversity of prey in the diet of geckos from that island (Hutcheson’s ttest, t= 2.72,
df = 254, p< 0.007), whereas diversities of invertebrates in the habitat and diet were similar
on Rey (t= 0.05, df = 101, p= 0.96).
3.5. Body Size and Body Condition of Geckos
There were not significant differences in the average body size of geckos between the
islands (SVL, mean
±
SE, Rey: 60.0
±
1.0 mm, n= 39; Isabel: 60.0
±
1.4 mm, n= 78; one-way
ANOVA, log
10
-transformed, F
1,115
= 0.27, p= 0.60). Considering the geckos that could be
reliably sexed, which were mainly adults, there were not significant differences in SVL
between sexes, although males tended to be larger (SVL, mean
±
SE, males: 64.5
±
1.5 mm,
n= 44; females: 60.4
±
1.3 mm, n= 39; one-way ANOVA, log
10
-transformed:
F1,81 = 3.11,
p= 0.08). Body mass depended strongly on tail condition and was not compared.
Tail break rates did not significantly differ between islands (% of regenerated tails:
Isabel = 65.4%, Rey = 61.5%;
χ2
= 0.17, p= 0.68), but significantly more females than males
had regenerated tails (males = 52.3%, females = 74.3%;
χ2
= 4.31, p= 0.037). Sex ratios were
significantly different between islands, with females being more abundant than males on
Rey, with the inverse occurring on Isabel (sex ratio, Rey: 11 males:18 females = 0.61; Isabel:
33 males:21 females = 1.57; χ2= 4.07, p= 0.044).
The body condition index (BCI) of geckos with their original tails was significantly
lower than that of geckos with fully grown regenerated tails (which, although they were
shorter, were much thicker at the basis) (BCI, mean
±
SE, entire tail:
−
0.130
±
0.023,
n= 42,
regenerated tail: +0.073
±
0.021, n= 75; two-way ANOVA: F
1,113
= 31.84, p< 0.0001), but
there were no significant differences between the islands (Rey: +0.002
±
0.025, n= 39;
Isabel:
−
0.001
±
0.024, n= 78; F
1,113
= 0.18, p= 0.67) and the interaction was not significant
(F1,113 = 0.15, p= 0.69).
Similarly, the scale mass index (SMI) did not significantly differ between islands
(SMI, mean
±
SE, Rey: 4.65
±
0.10, n= 39; Isabel: 4.54
±
0.11, n= 78; two-way ANOVA:
F1,113 = 0.10,
p= 0.75), nor did it depend significantly on the tail state (entire tail:
4.46 ±0.11,
n= 42, regenerated tail:
4.64 ±0.11,
n= 75; F
1,113
= 2.12, p= 0.15). Additionally, the
interaction was not significant (F1,113 = 1.88, p= 0.17).
4. Discussion
We found some differences in microhabitat characteristics between islands. They likely
resulted from anthropic disturbance and could further explain the differences observed
in diversity, but not in abundance, of invertebrates available in those habitats. These
differences in prey availability were reflected in the differences of the diversity of prey
consumed by T. mauritanica geckos. However, geckos seemed to respond with flexibility,
modifying the patterns of prey selection to maintain their diet composition. This probably
allowed geckos to maintain their body condition, regardless of anthropic habitat alterations.
The patches of seminatural habitats that remained, scattered between buildings, on
the human-inhabited island (Isabel) were apparently similar to the natural habitats of
the uninhabited island (Rey) and held high densities of T. mauritanica geckos and other
species of reptiles [
25
]. However, a detailed examination of microhabitat structure revealed
that seminatural habitats had suffered a clearing of bushes, which had been replaced
by more extended grassy areas. Additionally, the substrate was more compact, which
was likely due to an effect of erosion and trampling. Nevertheless, the proportion of
rocks that geckos could use as a refuge remained similar. Moreover, on the island with
human influence, geckos were also found under artificial rests, such as bricks or roof tiles,
which also provided cover and may have even favored the apparent high abundance of T.
mauritanica in this island. In fact, the use of artificial covers provided by researchers had
been used as a management measure for other species of saxicolous lizards and geckos [
51
].
These changes in microhabitat structure, in likely combination with other indeter-
minate human influences, can very likely explain the changes observed in the available

Animals 2023,13, 1413 10 of 14
invertebrates. Although the total abundance of invertebrates did not change between natu-
ral and seminatural habitats, there were differences in the abundances of each invertebrate
type. Some invertebrate types seemed to be favored by human disturbance and were more
abundant in seminatural habitats (e.g., isopods and gastropods), while other decreased
their numbers (e.g., beetles and ants), leading to low values of diversity, and probably a
loss of species. This is an expected effect of human disturbance. Indeed, many studies have
highlighted that human global alterations are leading to a mass loss of many invertebrates
and identified the drivers of this decline [
52
]. Human alterations may also favor that pest
insect populations flourish in urban areas [
53
]. Nevertheless, for a generalist predator, such
as T. mauritanica geckos, the loss of diversity and complexity of the invertebrate fauna
might not be important if the few remaining species, or the new pest ones, maintain high
numbers and are still appropriate as prey.
The diet composition of T. mauritanica on these islands was similar to those observed
in other Mediterranean populations [
19
–
24
], including some ground-dwelling arthropods
(mainly beetles, spiders and larvae) but also flying ones (especially on the uninhabited
island). Interestingly, considering the main prey types, there were not substantial differ-
ences between islands, which showed a very high overlap in diet composition. Hence, it
seemed that geckos were able to maintain their diet in spite of habitat anthropic alterations,
at least during the favorable spring season. However, seasonal changes in invertebrate
availability, such as the drastic decreases in abundance and diversity due to the summer
drought periods [
54
], potentially had a greater impact on the altered habitats, impeding
geckos from attaining their dietary requirements. Moreover, even in spring, the diversity
of prey types in the diet and the food niche breadth were already lower on the inhabited
island with altered habitats. Similarly, a previous study also showed that the diet of T.
mauritanica was more varied in rural areas than in cities [
55
]. Additionally, rock agamas
from urban areas, namely Psammophilus dorsalis, hada broader range of prey items as they
magnified their myrmecophagous specialization in these urban habitats [
56
]. The question
that arises is whether a less diverse diet has the same nutritional value. Studies with captive
reptiles have shown that a more diverse diet ensures the ingestion of a broader range of
nutrients and limits the likelihood of nutritional disease occurrence [57].
The diet of T. mauritanica did not directly reflect the availability of invertebrates in the
habitat in any of the islands. Rather, geckos consistently selected some prey types, while
they avoided other invertebrates regardless of their abundance. Therefore, T. mauritanica
geckos showed clear food preferences, similar to those described in other populations [
23
].
Geckos might try to maintain these preferences on both islands, regardless of the state of
the habitat and the available prey. However, this could be a problem because inhabiting
the altered habitat, even for some preferred prey types (beetles and spiders), requires
that geckos make a stronger positive selection (i.e., probably a higher foraging effort).
In contrast, in the natural habitat, the relative availability of the preferred prey types is
more similar to their presence in the diet. Additionally, we cannot rule the possibility that
the preference of Isabel’s geckos for some prey types that are no longer abundant might
be due not only to habitat alterations but also to competition for the same food item by
other species (lizards, etc.) that might be favored by the anthropic influence and be more
abundant here [58,59].
Moreover, the diversities of prey available and consumed were similar in the unaltered
habitat. Conversely, in the altered habitat, the diversity of prey consumed was lower
than expected in relation to the availability of prey. Therefore, feeding requirements
of T. mauritanica geckos were constrained in some way in the altered habitat, as geckos
maintained their feeding preferences for prey that were less abundant, but avoided some
of the most abundant invertebrates found there. Other anthropophilic animal species were,
however, more able to exploit anthropogenic food sources, even those new food items
that are not found in natural diets but instead thrive in urban environments [
10
,
14
,
16
].
Nevertheless, it might be possible that our study population of T. mauritanica of seminatural

Animals 2023,13, 1413 11 of 14
areas had not yet entirely adapted to human disturbance, while “pure” urban populations
might have shown greater flexibility in feeding behavior.
In spite of all the potentially negative effects of anthropic alteration of the habitat,
T. mauritanica geckos seemed able to maintain a good health state, as suggested by their
similar body condition values on both islands. Human disturbance has been shown to affect
body condition in other reptiles. For example, deforestation affects tropical forest geckos,
Cyrtodactylus spp., with geckos having lower body condition in patches with low canopy
cover, which, although not examined, might be attributed to lower prey availability [
60
].
However, in rock lizards, Iberolacerta cyreni, the loss of body condition in altered habitats
was mainly explained by the increased use of costly behavioral strategies to cope with the
increased predation risk due to the human-induced loss of natural refuges [
61
]. In green
anole lizards Anolis carolinensis, the level of human habitat modification was correlated
with body condition of lizards, although only in females; however, this effect did not seem
to be directly related to changes in arthropod abundance or biomass [
15
]. Additionally, in
another study of T. mauritanica geckos, the lower body condition of geckos observed in
urban habitats, in comparison with rural areas, was explained as a consequence of pollution
by heavy metals, rather than by changes in diet [
55
]. In contrast, rural rock agamas, P.
dorsalis, had lower body conditions than urban lizards, despite the greater diversity of prey
types and the larger volume of food consumed [
56
]. This was explained by the higher
movement rates, with presumed associated higher energy expenditure, of lizards in rural
areas. Nevertheless, it has been suggested that in many species the body condition might
be poorly correlated with body lipid reserves, and that these levels of reserves would not
always be directly related to fitness [
62
]. Thus, it is likely that, in order to examine the
actual effects of human alterations on the health state of T. mauritanica geckos, it will be
necessary to consider several alternative physiological parameters (i.e., immune response,
stress levels, etc.) [34].
5. Conclusions
The small effects of human disturbances of natural habitats may induce alterations
of a habitat and its fauna that may be not so apparent at first sight, but that require
examination. This is important in a changing world scenario, because otherwise many
threats to biodiversity may be easily overlooked. In our study area, included in a nature
reserve, we found that these seminatural habitats may have significant alterations in the
microhabitat structure that likely, or at least partly, explain the changes in the invertebrate
fauna. Further, these changes should likely affect the diet of insectivorous predators, such
as that of the Moorish gecko, T. mauritanica. However, in spite of these changes, it seems that
this gecko species is able to cope with the potential negative effects of human alterations
and maintain abundant populations with similar body conditions to those possessed by
geckos from natural habitats. This flexibility in responses to human disturbances may
allow some species, such as this variety of gecko, to proliferate in human-transformed
habitats. However, it remains to be examined in greater detail how the different effects
and different levels of human alterations may affect the actual physiological health state of
apparently "anthropophilic" animals. This would allow researchers to make predictions
and take actions to minimize potential future conservation problems.
Author Contributions:
Conceptualization, J.M. and V.P.-M.; methodology, J.M. and V.P.-M.; formal
analysis, J.M.; investigation, J.M., J.O., R.G.-R., G.R.-R., A.P.-C. and V.P.-M.; writing—original draft
preparation, J.M.; writing—review and editing, J.M., J.O., R.G.-R., G.R.-R., A.P.-C. and V.P.-M.; funding
acquisition, J.M. All authors have read and agreed to the published version of the manuscript.
Funding:
This research was funded by the Spanish Ministerio de Ciencia e Innovación project
PID2021-122358NB-I00 (MCIN/AEI /10.13039/501100011033 and ERDF A way of making Europe).
Institutional Review Board Statement:
Captures and observations were performed under license
by the “Organismo Autónomo de Parques Nacionales” (Spain). All applicable international, national
and institutional (Consejo Superior de Investigaciones Científicas) guidelines for the care and use

Animals 2023,13, 1413 12 of 14
of animals were followed. The animal study protocol was approved by the “ComisiónÉtica de
Experimentación Animal (CEEA)” of the Museo Nacional de Ciencias Naturales, CSIC.
Informed Consent Statement: Not applicable
Data Availability Statement:
The data presented in this study are openly available in FigShare at
https://doi.org/10.6084/m9.figshare.22296838.
Acknowledgments:
We thank two anonymous reviewers for helpful comments and the field station
of the ZEC “Islas Chafarinas” for use of their facilities, and J.I. Montoya, J. Díaz, G. Martínez, A. Sanz,
F. López and A. Ruiz for support and friendship in the Islands.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Gilbert, O.L. The Ecology of Urban Habitats; Springer: Dordrecht, The Netherlands, 1989.
2. Walker, L.R. The Biology of Disturbed Habitats; Oxford Academic Press: Oxford, UK, 2011.
3. Wuerthner, G.; Crist, E.; Butler, T. Keeping the Wild; Island Press: Washington, DC, USA, 2014.
4.
Peres, C.A.; Barlow, J.; Laurance, W.F. Detecting anthropogenic disturbance in tropical forests. Trends Ecol. Evol.
2006
,21, 227–229.
[CrossRef] [PubMed]
5.
Pimm, S.L.; Jenkins, C.N.; Abell, R.; Brooks, T.M.; Gittleman, J.L.; Joppa, L.N.; Raven, P.H.; Roberts, C.M.; Sexton, J.O. The
biodiversity of species and their rates of extinction, distribution, and protection. Science
2014
,344, 1246752. [CrossRef] [PubMed]
6.
Locey, K.J.; Stone, P.A. Factors affecting range expansion in the introduced Mediterranean Gecko, Hemidactylus turcicus.J. Herpetol.
2006,40, 526–530. [CrossRef]
7.
Stabler, L.B.; Johnson, W.L.; Locey, K.J.; Stone, P.A. A comparison of Mediterranean Gecko (Hemidactylus turcicus) populations in
two temperate zone urban habitats. Urban Ecosyst. 2012,15, 653–666. [CrossRef]
8. Johnson, M.T.J.; Munshi-South, J. Evolution of life in urban environments. Science 2017,358, 6363. [CrossRef]
9. Szulkin, M.; Munshi-South, J.; Charmantier, A. Urban Evolutionary Biology; Oxford University Press: New York, NY, USA, 2020.
10.
Lowry, H.; Lill, A.; Wong, B.B.M. Behavioural responses of wildlife to urban environments. Biol. Rev.
2013
,88, 537–549. [CrossRef]
[PubMed]
11. Wong, B.B.M.; Candolin, U. Behavioral responses to changing environments. Behav. Ecol. 2015,26, 665–673. [CrossRef]
12.
Stroud, J.T.; Colom, M.; Ferrer, P.; Palermo, N.; Vargas, V.; Cavallini, M.; Lopez, J.; Jones, I. Behavioral shifts with urbanization
may facilitate biological invasion of a widespread lizard. Urban Ecosyst. 2019,22, 425–434. [CrossRef]
13.
Pellitteri-Rosa, D.; Bellati, A.; Cocca, W.; Gazzola, A.; Martín, J.; Fasola, M. Urbanization affects refuge use and habituation to
predators in a polymorphic lizard. Anim. Behav. 2017,123, 359–367. [CrossRef]
14.
Sol, D.; Griffin, A.S.; Bartomeus, I.; Boyce, H. Exploring or avoiding novel food resources? The novelty conflict in an invasive bird.
PLoS ONE 2011,6, 0019535. [CrossRef]
15.
Battles, A.C.; Whittle, T.K.; Stehle, C.M.; Johnson, M.A. Effects of human land use on prey availability and body condition in the
green anole lizard, Anolis carolinensis.Herpetol. Conserv. Biol. 2013,8, 16–26.
16.
Peterson, M.; Baglieri, M.; Mahon, K.; Sarno, R.J.; Ries, L.; Burman, P.; Grigione, M.M. The diet of coyotes and red foxes in
Southern New York. Urban Ecosyst. 2021,24, 1–10. [CrossRef]
17.
Salvador, A. Salamanquesa común—Tarentola mauritanica. In Enciclopedia Virtual de los Vertebrados Españoles; Salvador, A., Marco, A.,
Eds.; Museo Nacional de Ciencias Naturales, CSIC: Madrid, Spain, 2016; Available online: http://www.vertebradosibericos.org/
(accessed on 15 February 2023).
18.
Seva, E. Densidad, distribución y reparto de recursos entre dos especies de saurios de la isla Plana (Alicante, España). Bull. Ecol.
1988,19, 357–362.
19.
Martínez-Rica, J.P. Contribución al estudio de la biología de los gecónidos ibéricos (Rept., Sauria). Publ. Centro Piren. Biol. Exp.
1974,5, 1–291.
20.
Gil, M.J.; Pérez-Mellado, V.; Guerrero, F. Eine vergleichende studie des nahrungserwerbs von Tarentola mauritanica (Reptilia:
Gekkonidae) in habitaten auf dem festland und auf inseln. Sauria 1993,15, 9–17.
21.
Gil, M.J.; Guerrero, F.; Pérez-Mellado, V. Seasonal variation in diet composition and prey selection in the Mediterranean gecko
Tarentola mauritanica.Israel J. Zool. 1994,40, 61–74.
22.
Hódar, J.A.; Pleguezuelos, J.M. Diet of the moorish gecko Tarentola mauritanica in an arid zone of south-eastern Spain. Herpetol. J.
1999,9, 29–32.
23.
Hódar, J.A.; Pleguezuelos, J.M.; Villafranca, C.; Fernández-Cardenete, J.R. Foraging mode of the Moorish gecko Tarentola
mauritanica in an arid environment: Inferences from abiotic setting, prey availability and dietary composition. J. Arid Environ.
2006,65, 83–93. [CrossRef]
24.
Capula, M.; Luiselli, L. Trophic niche overlap in sympatric Tarentola mauritanica and Hemidactylus turcicus: A preliminary study.
Herpetol. J. 1994,4, 24–25.
25.
García-Roa, R.; Ortega, J.; López, P.; Civantos, E.; Martín, J. Revisión de la distribución y abundancia de la herpetofauna en las
Islas Chafarinas: Datos históricos vs. tendencias poblacionales. Bol. Asoc. Herpetol. Esp. 2014,25, 55–62.

Animals 2023,13, 1413 13 of 14
26.
Martín, J.; López, P.; García, L.V. Soil characteristics determine microhabitat selection of the fossorial amphisbaenian Trogonophis
wiegmanni.J. Zool. 2013,290, 265–272. [CrossRef]
27.
Herrick, J.E.; Jones, T.L. A dynamic cone penetrometer for measuring soil penetration resistance. Soil Sci. Soc. Am. J.
2002
,66,
1320–1324. [CrossRef]
28.
Martín, J.; Salvador, A. Tail loss and foraging tactics of Iberian rock-lizards, Lacerta monticola.Oikos
1993
,66, 318–324. [CrossRef]
29.
Goldsbrough, C.L.; Hochuli, D.F.; Shine, R. Invertebrate biodiversity under hot rocks: Habitat use by the fauna of sandstone
outcrops in the Sydney region. Biol. Conserv. 2003,109, 85–93. [CrossRef]
30.
Martín, J.; Ortega, J.; López, P.; Pérez-Cembranos, A.; Pérez-Mellado, V. Fossorial life does not constrain diet selection in the
amphisbaenian Trogonophis wiegmanni.J. Zool. 2013,291, 226–233. [CrossRef]
31.
Green, A.J. Mass/length residuals: Measures of body condition or generation of spurious results? Ecology
2000
,82, 1473–1483.
[CrossRef]
32.
Schulte-Hostedde, A.I.; Zinner, B.; Millar, J.S.; Hickling, G.J. Restitution of mass-size residuals: Validating body condition indices.
Ecology 2005,86, 155–163. [CrossRef]
33.
Peig, J.; Green, A.J. New perspectives for estimating body condition from mass/length data: The scaled mass index as an
alternative method. Oikos 2009,118, 1883–1891. [CrossRef]
34. Wikelski, M.; Cooke, S.J. Conservation physiology. Trends Ecol. Evol. 2006,21, 38–46. [CrossRef]
35.
Brischoux, F.; Rolland, V.; Bonnet, X.; Caillaud, M.; Shine, R. Effects of oceanic salinity on body condition in sea snakes. Integr.
Comp. Biol. 2012,52, 235–244. [CrossRef]
36.
Angelici, F.M.; Luiselli, L.; Rugiero, L. Food habits of the green lizard, Lacerta bilineata, in central Italy and a reliability test of
faecal pellet analysis. Ital. J. Zool. 1997,64, 267–272. [CrossRef]
37.
Suarez, A.V.; Richmond, J.Q.; Case, T.J. Prey selection in horned lizards following the invasion of Argentine ants in southern
California. Ecol. Appl. 2000,10, 711–725. [CrossRef]
38.
Hawlena, D.; Pérez-Mellado, V. Change your diet or die: Predator-induced shifts in insectivorous lizard feeding ecology. Oecologia
2009,161, 411–419. [CrossRef] [PubMed]
39.
Pérez-Cembranos, A.; León, A.; Pérez-Mellado, V. Omnivory of an insular lizard: Sources of variation in the diet of Podarcis lilfordi
(Squamata, Lacertidae). PLoS ONE 2016,11, e0148947. [CrossRef]
40.
Pincheira-Donoso, D. Testing the accuracy of fecal based analyses in studies of trophic ecology of lizards. Copeia
2008
,2008,
322–325. [CrossRef]
41.
Pérez-Mellado, V.; Pérez-Cembranos, A.; Garrido, M.; Luiselli, L.; Corti, C. Using faecal samples in lizard dietary studies.
Amphibia-Reptilia 2011,32, 1–7. [CrossRef]
42.
Alemany, I.; Pérez-Cembranos, A.; Castro, J.A.; Picornell, A.; Pérez-Mellado, V.; Ramon, C. Diet of the insular lizard, Podarcis
lilfordi (Günther, 1874): Complementary morphological and molecular approaches. Animals 2023,13, 507. [CrossRef]
43. Magurran, A.E. Ecological Diversity and Its Measurement; Croom Helm: London, UK, 1988.
44. Hutcheson, K. A test for comparing diversities based on the Shannon formula. J. Theor. Biol. 1970,29, 151–154. [CrossRef]
45. Pianka, E.R. The structure of lizard communities. Annu. Rev. Ecol. Syst. 1973,4, 53–74. [CrossRef]
46. Ivlev, V.S. Experimental Ecology of the Feeding of Fishes; Yale University Press: New Haven, CT, USA, 1961.
47.
Jacobs, J. Quantitative measurements of food selection; a modification of the forage ratio and Ivlev’s selectivity index. Oecologia
1974,14, 413–417. [CrossRef]
48. Lechowicz, M.J. The sampling characteristics of electivity indices. Oecologia 1982,52, 22–30. [CrossRef]
49.
Vanderploeg, H.A.; Scavia, D. Calculation and use of selectivity coefficients of feeding: Zooplankton grazing. Ecol. Model.
1979
,7,
135–149. [CrossRef]
50. Sokal, R.R.; Rohlf, F.J. Biometry, 3rd ed.; W.H. Freeman and Co: New York, NY, USA, 1995.
51.
Webb, J.K.; Shine, R. Paving the way for habitat restoration: Can artificial rocks restore degraded habitats of endangered reptiles?
Biol. Conserv. 2000,92, 93–99. [CrossRef]
52.
Sánchez-Bayo, F.; Wyckhuys, K.A.G. Worldwide decline of the entomofauna: A review of its drivers. Biol. Conserv.
2019
,232,
8–27. [CrossRef]
53. Robinson, W.H. Urban Entomology: Insect and Mite Pests in the Human Environment; Chapman & Hall: London, UK, 1996.
54.
Martín, J.; Ortega, J.; García-Roa, R.; Rodríguez-Ruiz, G.; Pérez-Cembranos, A.; Pérez-Mellado, V. Coping with drought? Effects
of extended drought conditions on soil invertebrate prey and diet selection by a fossorial amphisbaenian reptile. Curr. Zool.
2022
.
[CrossRef]
55.
Fletcher, D.E.; Hopkins, W.A.; Standora, M.M.; Arribas, C.; Baionno-Parikh, J.A.; Saldaña, T.; Fernández-Delgado, C. Geckos as
indicators of urban pollution. In Urban Herpetology. Herpetological Conservation 3; Mitchell, J.C., Jung Brown, R.E., Bartholomew,
B., Eds.; Society for the Study of Amphibians and Reptiles: Salt Lake City, UT, USA, 2008; pp. 225–237.
56.
Balakrishna, S.; Batabyal, A.; Thaker, M. Dining in the city: Dietary shifts in Indian rock agamas across an urban–rural landscape.
J. Herpetol. 2016,50, 423–428. [CrossRef]
57. Courteney-Smith, J. The Arcadia Guide to Reptile and Amphibian Nutrition; Arcadia Reptile: Ely, UK, 2014.
58.
Dunham, A.E. An experimental study of interspecific competition between the iguanid lizards Sceloporus merriami and Urosaurus
ornatus.Ecol. Monogr. 1980,50, 309–330. [CrossRef]

Animals 2023,13, 1413 14 of 14
59.
Rodriguez Curras, M.; Donadio, E.; Middleton, A.D.; Pauli, J.N. Carnivore niche partitioning in a human landscape. Am. Nat.
2022,199, 496–509. [CrossRef]
60.
Aksornneam, A.; Sung, Y.H.; Aowphol, A. Effect of habitat structure on abundance and body conditions of two sympatric geckos,
Cyrtodactylus saiyok and Cyrtodactylus tigroides, in the karst forest of western Thailand. J. Nat. Hist. 2023,57, 395–407. [CrossRef]
61.
Amo, L.; López, P.; Martín, J. Habitat deterioration affects body condition of lizards: A behavioral approach with Iberolacerta
cyreni lizards inhabiting ski resorts. Biol. Conserv. 2007,135, 77–85. [CrossRef]
62.
Wilder, S.M.; Raubenheimer, D.; Simpson, S.J. Moving beyond body condition indices as an estimate of fitness in ecological and
evolutionary studies. Funct. Ecol. 2016,30, 108–115. [CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.