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Galapagos sea lions' population and pup abundance trend in the Galapagos Archipelago from 2014 to 2018. It includes the annual counts at 32 breeding rookeries on 13 islands distributed throughout the archipelago. Blue and gray circles show the total population and pup population, respectively. Blue and gray dashed lines show the population trend and the pup trend, respectively.
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Currently, the Galapagos sea lion (GSL, Zalophus wollebaeki) and Galapagos fur seal (GFS, Arctocephalus galapagoensis) are among the most important endemic species for conservation in the Galapagos Archipelago. Both are classified as “Endangered” since their populations have undergone drastic declines over the last several decades. In this study we...
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... counted, representing an estimated 19,929 (95% confidence interval (CI) = 17,617-24,694) animals in total. The greater abundance was estimated in 2014 (21,493; 95% CI = 18,864-26,895 individuals), based on a count of 4,980 animals. Overall, there was a decrease of 23.9% in the number of animals counted from 2014 to 2015 across the archipelago (Fig. 2); whereas from 2015 to 2018 the total of animals counted increased 29%. The average annual growth rate in the archipelago was 1% (slope = 0.01, standard error (SE) = 0.04, p = 0.818, R 2 = 0.02) between 2014 and 2018 ( Fig. ...
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... animals. Overall, there was a decrease of 23.9% in the number of animals counted from 2014 to 2015 across the archipelago (Fig. 2); whereas from 2015 to 2018 the total of animals counted increased 29%. The average annual growth rate in the archipelago was 1% (slope = 0.01, standard error (SE) = 0.04, p = 0.818, R 2 = 0.02) between 2014 and 2018 ( Fig. ...
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... coefficient of variation (CV) = 82.5%) and central (CV = 33.4%) rookeries, respectively ( Table 2). The pup abundance in the archipelago decreased 40.5% between 2014 and 2016, whereas from 2015 to 2018 it increased 91.5%. The average annual growth rate of pup abundance was 5% between 2014 and 2018 (slope = 0.05, SE = 0.11, p = 0.677, R 2 = 0.07) (Fig. 2). This increasing pup trend between 2014 and 2018 was observed in northern and central rookeries at an average annual rate of 100.3% (slope = 0.69, SE = 0.22, p = 0.050, R 2 = 0.77) and 12.9% (slope = 0.12, SE = 0.07, p = 0.183, R 2 = 0.50), respectively. In the west, pups decreased at an average rate of − 6.7% (slope = − 0.07, SE = ...
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... the central region (4.1 ± 0.4%). The average annual growth rate in the western rookeries was 3.3% (slope = 0.03, SE = 0.10, p = 0.772, R 2 = 0.03) between 2014 to 2018, while for the northern and central rookeries it was 3.9% (slope = 0.04, SE = 0.07, p = 0.637, R 2 = 0.08) and −0.2% (slope = −0.01, SE = 0.07, p = 0.975, R 2 = 0.01) respectively (Fig. ...
Citations
... The Galapagos' extant biotic components are potentially threatened by habitat degradation, food-supply depletion, invasive species and climate change. Concerning the last, awareness about the vulnerability of certain taxa has emerged following studies of the El Niño-La Niña system's impact on low-population species (e.g., Grant et al. 2000;Vargas et al. 2007Vargas et al. , 2008Tindle et al. 2013;Karnauskas et al. 2015;Páez-Rosas et al. 2021). As a consequence, the superposed threat of anthropogenic climate change has led some to outline related conservation strategies (e.g., Dueñas et al. 2021). ...
Our focus is the colonization history of the Galápagos’ vertebrate clades: 11 land-bound groups (eight reptiles, three rodents) and 13 taxa of flyers and swimmers (ten winged birds, two pinnipeds, one penguin). Using ‘colonization intervals’ and ‘colonization profiles’, it is clear that the two sets of taxa assembled very differently. The former includes older clades with between one, and potentially eight, predating the emergence of the oldest island (4 Mya). For the origin of some lineages, now-sunken landmasses associated with the Galápagos mantle-plume hotspot must have been involved, but for others it could reflect taxonomic uncertainties. In contrast, the taxa of flyers and swimmers are markedly younger, indicating either higher rates of colonization and extirpation for these sorts of animal, or continued genetic influx from mainland populations, or some combination of both factors. Concerning the first, possible drivers are the environmental stressors associated with the El Niño–La Niña climate system; the recent clades may be vulnerable to extreme events within the oscillation sequence, perhaps on ≥104-year timescales. Therefore, loose temporal thresholds might exist for the archipelago’s vertebrate groups beyond which selection fortifies them from the most challenging of seasonal states. Moreover, in a world of climate uncertainty, the findings appear relevant to conservation initiatives suggesting a focusing on the younger elements within the Galápagos’ biota.
... The five localities are shown with a red triangle and bathymetry contour lines (100 m intervals) between islands. The size of the triangle is proportional to population sizes according toPáez-Rosas et al. (2021 with default settings; (e) quality filter- ...
Tropical ecosystems are challenging for pinnipeds due to fluctuating food availability. According to previous research, the Galapagos sea lion (GSL, Zalophus wollebaeki) adopts trophic flexibility to face such conditions. However, this hypothesis comes from studies using traditional methods (hard-parts analysis of scat and isotopic analysis from tissue). We studied the diet of five rookeries in the southeastern Galapagos bioregion (which harbors the highest GSL density), via DNA-metabarcoding of scat samples. The DNA-metabarcoding approach may identify consumed prey with a higher taxonomic resolution than isotopic analysis, while not depending on hard-parts remaining through digestion. Our study included five different rookeries to look for evidence of trophic flexibility at the bioregional level. We detected 98 prey OTUs (124 scats), mostly assigned to bony-fish taxa; we identified novel prey items, including a shark, rays, and several deep-sea fish. Our data supported the trophic flexibility of GSL throughout the studied bioregion since different individuals from the same rookery consumed prey coming from different habitats and trophic levels. Significant diet differentiations were found among rookeries, particularly between Punta Pitt and Santa Fe. Punta Pitt rookery, with a more pronounced bathymetry and lower productivity, was distinguished by a high trophic level and consumption of a high proportion of deep-sea prey; meanwhile, Santa Fe, located in more productive, shallow waters over the shelf, consumed a high proportion of epipelagic planktivorous fish. Geographic location and heterogeneous bathymetry of El Malecon, Española, and Floreana rookeries would allow the animals therein to access both, epipelagic prey over the shelf, and deep-sea prey out of the shelf; this would lead to a higher prey richness and diet variability there. These findings provide evidence of GSL adopting a trophic flexibility to tune their diets to different ecological contexts. This strategy would be crucial for this endangered species to overcome the challenges faced in a habitat with fluctuating foraging conditions.
... Large-scale monitoring in the Galápagos is logistically extremely challenging and is therefore rare (Páez-Rosas et al., 2021;Vargas et al., 2005). For most of the species, the majority of studies focus on just a few colonies (Ortiz-Catedral et al., 2023;Valle, 1995). ...
Population surveys are vital for wildlife management, yet traditional methods often demand excessive time and resources, leading to data gaps for many species. Modern technologies such as drones can facilitate field surveys but may also increase data analysis challenges. Citizen Science (CS) can address this issue by engaging non-specialists for data collection and analysis. We evaluated CS for population monitoring using the endangered Galapagos marine iguana as a case study, assessing online volunteers' ability to detect and count animals in aerial images. Comparing against a Gold Standard dataset of expert counts in 4345 images, we explored optimal aggregation methods from CS inputs, considering image quality and filtering data from infrequent and anonymous participants. During three phases of our project - hosted on the Zooniverse platform - over 13,000 volunteers made 1,375,201 classifications from 57,838 aerial images; each being independently classified 20 (phases 1 & 2) or 30 (phase 3) times. Volunteers achieved 68% to 94% accuracy in detecting iguanas, with more false negatives than false positives. Image quality strongly influenced accuracy; by excluding data from suboptimal pilot-phase images, volunteers counted with 90% to 92% of accuracy. For detecting presence or absence of iguanas, the commonly used "majority vote" aggregation approach (where the answer selected is that given by the majority of individual inputs) produced less accurate results than when a minimum threshold of five (from the 20/30 independent classifications) was used. For counting iguanas, HDBSCAN clustering yielded the best results. Excluding inputs from anonymous and inexperienced volunteers decreased accuracy. We conclude that online volunteers can accurately identify and count marine iguanas from drone images, though a tendency to underestimate warrants further consideration. CS-based data analysis is faster than manual counting but still resource-intensive, underscoring the need to develop a Machine Learning approach.
... The endemic Galapagos sea lion (GSL, Zalophus wollebaeki) has been listed as an endangered species in the International Union for Conservation of Nature Red List since 2008 due to a strong reduction in its population of more than 50% over the last four decades [1]. The main factors causing this decline are environmental variations and oceanographic warming events such as the El Niño-Southern Oscillation [2,3]; however, habitat degradation and pathogen transmissions by introduced and domestic species (i.e., rats, dogs and cats) have been identified as a potential conservation problem for this species [4,5]. ...
... Blood samples were collected from juvenile animals from the El Malecón rookery on San Cristóbal Island during the summer of 2016 (n = 46) and 2017 (n = 64). Juveniles are a representative sample of GSL populations, since they are the second most abundant sex/age category in rookeries [3,25]. In addition, the capture of juveniles represents a minor disturbance to wild animal rookeries. ...
Simple Summary
Over the last four decades, the Galapagos sea lion (GSL—Zalophus wollebaeki) has faced a significant population decline. An important concern is the increasing population of domestic dogs in some islands of the archipelago. These animals can be a source of various infectious diseases that can be transmitted to the GSL. An important pathogen is the canine distemper virus (CDV), causing the viral infection that generates the most concern for the agencies responsible for the management and conservation of the Galapagos pinnipeds. This virus was detected in the GSL in 2010; however, very little is known about its circulation and epidemiology. Our study tested 110 GSL serum samples that were collected during the summer of 2016 and 2017. Our results showed an increasing circulation of CDV and highlight the importance of monitoring emerging diseases that can be transmitted from the domestic to the wildlife species of the archipelago.
Abstract
Background: The emblematic Galapagos sea lion (GSL—Zalophus wollebaeki) has faced an important population decline over the last four decades. There are multiple environmental and biological factors that might be implied in this decrease. Recently, evidence of various zoonotic infectious diseases that can be potential threats has been reported. Considering that in some islands of the archipelago the risk of transmission of infectious diseases may be promoted by the increasing population of domestic dogs, epidemiological vigilance and search of new pathogens are essential. The canine distemper virus (CDV), one of the viral pathogens that generate the most concern for the agencies responsible for the management and conservation of the Galapagos pinnipeds, was detected in the GSL in 2010. However, there is scarce information about its impact on GSL health and about its epidemiology. Methods: In this study, 110 GSL serum samples were collected during the summer of 2016 and 2017. All samples were exposed to VERO dog SLAM cells expressing the canine SLAM receptor. Results: Our results showed a significative increase (p = 0.04) in the frequency of neutralizing antibodies to CDV in the 2017 (53.1%) samples compared to the 2016 samples (19.6%). Conclusions: Our work confirmed the continuous and increasing circulation of the CDV in the GSL and highlights the importance of monitoring emerging diseases that can be transmitted from domestic to wildlife species. Vigilance of CDV is essential to understand the role of this virus in GSL mortality and to take informed decisions for wildlife conservation.
... The Galapagos sea lion, Zalophus wollebaeki, and Galapagos fur seal, Arctocephalus galapagoensis, are endemic otariids of the archipelago that face different challenges to survive [3][4][5]. Environmental and anthropogenic factors impact the population dynamics of pinnipeds [6], so both species developed adaptation mechanisms allowing them to persist in the archipelago despite the ecosystem's uncertainty in terms of variability in feeding resources and climatic conditions [5,7] and human-induced pressures that contribute to the deterioration of their habitat [8,9]. ...
... The Galapagos sea lion is distributed throughout the archipelago, mainly on southeastern islands where 62% of its population is concentrated [9]. It is more numerous than the Galapagos fur seal and has a larger size, approximately 40% larger [7,36]. ...
... The Galapagos fur seal breeds on eight main rookeries on western and northern islands, with 95% of its population on Fernandina Island [9], which corresponds to Galapagos Pinnipeds, Challenges to Their Survival DOI: http://dx.doi.org /10.5772/intechopen.113366 ...
Pinnipeds endemic to the Galapagos archipelago are in endangered conservation
status. The Galapagos sea lion, Zalophus wollebaeki, and Galapagos fur seal,
Arctocephalus galapagoensis, have adapted to an ecosystem with high environmental
variability and unpredictable marine productivity to survive. In addition to the
environmental factors that pressure their populations, these species are exposed to
anthropogenic influence, mainly in rookeries on islands with human settlements.
It has been determined that the populations of Galapagos pinnipeds have different
growth trends between regions of the archipelago, islands of the same region, and
between rookeries of the same island. 58% of the Galapagos sea lion population is
in the southeastern, with the largest rookery in direct contact with the inhabitants.
Various strategies have been proposed to reduce the negative impacts of human–animal
interaction, ensure the population’s viability over time, and reduce the species’
extinction risk.
... During the past 30 years, the sea lion population has experienced a significant decline [2], leading to its current endangered status, as recognized by the International Union for Conservation of Nature (IUCN) [4]. This decline can be attributed to several factors, with strong oceanographic events such as the "El Niño" phenomenon being particularly impactful, resulting in approximately a 50% reduction in its population, which can take up to 7 years to recover [5], [6]. Additionally, the mortality of hatchlings increases to 100% during these environmental phenomena due to the reduction in the food supply on the islands [7]. ...
... The distribution of otariids comprises the coasts of North and South America, the coasts of North Asia, Australia, New Zealand, and in addition several island systems including the Galapagos archipelago (Wursig, Perrin & Thewissen, 2009). The Galapagos sea lion, Zalophus wollebaeki (Sivertsen, 1953), is an endemic and endangered otariid species (Trillmich, 2015), which concentrates its largest populations in the southeastern part of the archipelago (Riofrío-Lazo, Arreguín-Sánchez & Páez-Rosas, 2017;Páez-Rosas et al., 2021). Given its position as top predator and its high nutritional efficiency, it is considered as a sentinel species of the ecosystem (Páez-Rosas & Guevara, 2017), and its permanence in the region is assumed to regulate the health and functioning of the Galapagos marine ecosystem at all trophic levels (Fariña et al., 2003;. ...
Background
The Galapagos sea lion, Zalophus wollebaeki, is an endemic and endangered otariid, which is considered as a sentinel species of ecosystem dynamics in the Galapagos archipelago. Mitochondrial DNA is an important tool in phylogenetic and population genetic inference. In this work we use Illumina sequencing to complement the mitogenomic resources for Zalophus genus—the other two species employed Sanger sequencing—by a complete mitochondrial genome and a molecular clock of this species, which is not present in any case.
Materials and Methods
We used DNA obtained from a fresh scat sample of a Galapagos sea lion and shotgun-sequenced it on the Illumina NextSeq platform. The obtained raw reads were processed using the GetOrganelle software to filter the mitochondrial Zalophus DNA reads (∼16% survive the filtration), assemble them, and set up a molecular clock.
Results
From the obtained 3,511,116 raw reads, we were able to assemble a full mitogenome of a length of 16,676 bp, consisting of 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNA), and two ribosomal RNAs (rRNA). A time-calibrated phylogeny confirmed the phylogenetic position of Z. wollebaeki in a clade with Z. californianus, and Z. japonicus, and sister to Z. californianus; as well as establishing the divergence time for Z. wollebaeki 0.65 million years ago. Our study illustrates the possibility of seamlessly sequencing full mitochondrial genomes from fresh scat samples of marine mammals.
... Several other research expeditions have been undertaken in Galaṕagos with the explicit purpose of studying cetaceans since then (Lyrholm et al., 1992;Smith and Whitehead, 1999;Palacios, 1999a;Palacios, 2000;Wise et al., 2009;Feĺix et al., 2011;Biggs et al., 2017;O'Hern et al., 2017). With the establishment of the GMR, since the early 2000s collaborative efforts between Galaṕagos-based and international scientists have continued to generate crucial knowledge about marine mammals in the area (Palacios and Salazar, 2002;Palacios et al., 2004;Denkinger et al., 2013;Biggs et al., 2017;O'Hern et al., 2017;Eguiguren et al., 2019;Denkinger et al., 2020;Eguiguren et al., 2021;Paéz-Rosas et al., 2021). Finally, cetacean presence in Galaṕagos has also been gleaned from documentation of live-stranding events, beach-cast specimens, and osteological specimens in museums (Palacios, 1996;Palacios et al., 2004). ...
... Knowledge gap Unlike pinnipeds, for which population assessments have been conducted on a regular basis throughout Galaṕagos (e.g., Paéz-Rosas et al., 2021), very few studies have reported population assessments for cetaceans in Galaṕagos (Palacios and Forney, 2008;O'Hern et al., 2017;Whitehead and Shin, 2022), and there is no formal ongoing program for monitoring cetacean populations. Yet, baseline information on demographic parameters, such as density, abundance, survival, and recruitment, is essential for understanding population status and dynamics, and to unravel the relative importance of competition and predation in structuring the local cetacean community relative to the influences of environmental variability. ...
... Other than basic documentation of stranding events , health assessments for cetaceans in Galaṕagos are absent. Studies have shown that environmental perturbations such as El Niño as well as exposure to anthropogenic activities near human population centers have impacts on the body condition and general health of teleost fish (Lamb et al., 2018) and pinnipeds (Brock et al., 2013a;Brock et al., 2013b;Paeź-Rosas et al., 2016;Paéz-Rosas et al., 2021), suggesting that cetaceans may also be affected by these stressors. ...
... The largest GSL rookeries are located on the southeast islands of the archipelago (i.e., Española, Floreana, San Cristobal, and Santa Fe), with an estimated population of 2300 to 4100 individuals (Riofrío-Lazo et al., 2017;Páez-Rosas et al., 2021). The trophic efficiency of this region is significantly influenced by Humboldt current, which provides cold and highly productive waters . ...
Marine debris pollution poses a significant global threat to biodiversity, with plastics being the primary debris type found in oceans due to their low-cost production and high demand worldwide. Microplastics (MPs, <5 mm in size) are highly bioavailable to a wide range of marine taxa, including marine mammals, through direct and indirect ingestion routes (i.e., trophic transfer). Recently, MP pollution has been detected on the Galapagos Marine Reserve, so in this study we developed a baseline framework for MP pollution in the Galapagos sea lion (GSL, Zalophus wollebaeki) through scat-based analysis. We collected 180 GSL scat samples from the southeast region following strict quality assurance/quality control protocols to detect, quantify and characterize physical-chemical properties of MPs through visual observations and μFT-IR spectroscopy. We recovered 81 MPs of varying sizes and colors in 37 % of samples (n = 66), consisting mostly of fibers (69 %, x̄=0.31 ± 0.57 particles scat−1). The number of particles per gram of sample wet weight ranged from 0.02 to 0.22 (x̄=0.04 ± 0.05 particles scat wet g−1). El Malecón and Punta Pitt rookeries at San Cristobal Island had the highest number of MPs (x̄=0.67 ± 0.51 and 0.43 ± 0.41 particles scat−1, respectively), and blue-colored particles were the most common in all samples. We identified eleven polymers in 46 particles, consisting mostly of polypropylene-polyethylene copolymer, polypropylene, cellulose, polyethylene, and polyvinyl chloride. The textile, fishing, and packaging industries are likely significant sources of microfibers into this insular ecosystem. Our results suggest that the GSL is exposed to MPs due to anthropogenic contamination and bioaccumulation associated with trophic processes. These findings provide an important baseline framework and insights for future research on MP pollution in the region, as well as for management actions that will contribute to the long-term conservation of the GSL.
... Primarily found in the Galápagos Islands archipelago, Z. wollebaeki often congregates in small groups on Isla de la Plata off mainland Ecuador (Melin et al. 2018). Considered Endangered by the International Union for Conservation of Nature (IUCN) (Trillmich 2015), the species has been negatively affected by anthropogenic pressures such as introduced diseases and the increasing frequency of El Niño events linked to climate change (Melin et al. 2018;Krüger et al. 2021;Páez-Rosas et al. 2021). In 2018, a limited population size of 17 000-24 000 individuals was reported after a decline of 23.8% in 2015, a year with an El Niño event (Páez-Rosas et al. 2021). ...
... Considered Endangered by the International Union for Conservation of Nature (IUCN) (Trillmich 2015), the species has been negatively affected by anthropogenic pressures such as introduced diseases and the increasing frequency of El Niño events linked to climate change (Melin et al. 2018;Krüger et al. 2021;Páez-Rosas et al. 2021). In 2018, a limited population size of 17 000-24 000 individuals was reported after a decline of 23.8% in 2015, a year with an El Niño event (Páez-Rosas et al. 2021). As the number and intensity of El Niño events increases, Z. wollebaeki is also facing decreasing pup abundance, further impacting the species' survivability and conservation status (Páez-Rosas et al. 2021). ...
... In 2018, a limited population size of 17 000-24 000 individuals was reported after a decline of 23.8% in 2015, a year with an El Niño event (Páez-Rosas et al. 2021). As the number and intensity of El Niño events increases, Z. wollebaeki is also facing decreasing pup abundance, further impacting the species' survivability and conservation status (Páez-Rosas et al. 2021). ...
The endangered Galápagos sea lion ( Zalophus wollebaeki ) inhabits the Galápagos Islands off the coast of Ecuador. We present a complete mitochondrial genome (16 465 bp) of a female paratype from the collections of the Natural History Museum Oslo, Norway, assembled from next-generation sequencing reads. It contains all canonical protein-coding, rRNA, tRNA genes, and the D-loop region. Sequence similarity is 99.93% to a previously published conspecific mitogenome sequence and 99.37% to the mitogenome sequence of the sister species Z. californianus . Sequence similarity of the D-loop region of the Z. wollebaeki paratype mitogenome is >99%, while the sequence difference to the Z. californianus sequences exceeds 2.5%. The paratype mitogenome sequence supports the taxonomic status of Z. wollebaeki as a separate species.
