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Varanus indicus on Saipan. The population on Saipan was described as V. tsukamotoi by Kashida in 1929; later, this taxon was placed as a synonym of V. indicus by Mertens in 1942. Photograph by Peter Bonser .
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... In addition, the heath goanna may be an effective biological control K E Y W O R D S ecosystem function, ecosystem services, introduced species, reptiles, rewilding, scavenging (Cota, 2008;Greer, 1989;Mirtschin, 1982;Robinson et al., 1985;Uchida, 1966). ...
Human‐induced environmental change has caused widespread loss of species that support important functions for ecosystems and society. For example, vertebrate scavengers contribute to the functional health of ecosystems and provide services to agricultural landscapes by removing carcasses and associated pests. Widespread extirpation of native Australian mammals since the arrival of Europeans in Australia has removed many scavenging species from landscapes, while scavenging mammals such as European red foxes (Vulpes vulpes) have been introduced. In much of Australia, squamate reptiles are the largest native terrestrial scavengers remaining, where large native mammals are extinct and conservation management is being undertaken to remove invasive mammals. The contribution of reptiles to scavenging functions is not well understood. In this study, we investigated the ecosystem functions provided by large reptiles as scavengers to better understand how populations can be managed to support ecosystem services. We investigated the ecosystem services provided by vertebrate scavengers in Australian coastal mallee ecosystems, focusing on the heath goanna (Varanus rosenbergi), the only extant native terrestrial scavenger in the region. We carried out exclosure experiments, isolating the scavenging activity of different taxonomic groups to quantify the contribution of different taxa to scavenging services, specifically the removal of rat carcasses, and its impact on the occurrence of agriculturally damaging blowflies. We compared areas with different native and invasive scavenger communities to investigate the impact of invasive species removal and native species abundance on scavenging services. Our results indicated that vertebrate scavenging significantly contributes to carcass removal and limitation of necrophagous fly breeding in carcasses and that levels of removal are higher in areas associated with high densities of heath goannas and low densities of invasive mammals. Therefore, augmentation of heath goanna populations represents a promising management strategy to restore and maximize scavenging ecosystem services.
... Table 3 Best phylogenetic linear models, evaluating the association between area dispersal variables (see Table 1 possibly through the accidental use of vegetation rafts, both by adults or egg-clutches (Gibbons & Zug, 1987;Goldberg et al., 2011). At least one large species, Varanus indicus, could also have colonized numerous islands naturally (Cota, 2008;Weijola et al., 2019) because its large size and salt tolerance may have allowed it to survive vast journeys across the sea (e.g., due to the increased fasting capacity of large-bodied species; Jaffe et al., 2011). ...
The Pacific Ocean is the largest in the world, and it contains many remote archipelagos, some of which are distant more than 4000 km from continents. Despite their isolation, these archipelagos harbour diverse assemblages of squamate reptiles (lizards and snakes), and these species differ greatly in their dispersal ranges. This study tested the hypothesis that there is a spatial effect on the variation among species in dispersal ability and that it is also associated with the evolutionary relationships among species and their life‐history strategies (body size and reproductive mode). The results indicated greater spatial than phylogenetic effects on the variables describing interspecific dispersal. The unisexual reproduction mode in squamates is not associated with a greater ability to colonize than sexual species that rely on similar mechanisms of dispersal. The higher reproductive rate of unisexual taxa might be initially advantageous for establishment on remote oceanic islands because of the unlikely arrival of sexual congenerics, which are frequently superior competitors in island ecosystems. Body size tends to exert a negative effect on the dispersal capacity of island squamates, but this relationship is positive in a subgroup of recently introduced commensal species.
... Since a number of forms within the Varanus indicus species group appear to represent independent evolutionary lineages and may therefore be island endemics, the likely future discovery of new species may affect the conservation status of this geographically widespread species. For monitors in the Caroline and Mariana Islands, future study of molecular and morphological similarities and differences to distant populations will help in elucidating whether the species occurs naturally on these islands or was introduced (Cota 2008). The latter seems unlikely, since monitor lizards have a long tradition in the history and mythology of the indigenous Chamorro people from Guam (Cunningham and Beaty 2001). ...
... Since a number of forms within the Varanus indicus species group appear to represent independent evolutionary lineages and may therefore be island endemics, the likely future discovery of new species may affect the conservation status of this geographically widespread species. For monitors in the Caroline and Mariana Islands, future study of molecular and morphological similarities and differences to distant populations will help in elucidating whether the species occurs naturally on these islands or was introduced (Cota 2008). The latter seems unlikely, since monitor lizards have a long tradition in the history and mythology of the indigenous Chamorro people from Guam (Cunningham and Beaty 2001). ...
available at https://www.iucnredlist.org/species/200972722/1533318
... Many scientists have regarded these remote populations as human introductions, either by aboriginal populations [9], the German colonial administration prior to WWI [10], or later by the Japanese colonial administration [10][11][12][13]. However, based on linguistic evidence and nineteenth-century literature records, Cota [14] argued for either natural colonizations or human-mediated introductions by early Micronesian settlers, at least for populations in the Mariana Islands. ...
... Tail banding varies from weak to non-existent. Photographs of live animals [9,14] (figures 6 and 7) show them to have a black ground colour with bright yellow spots, the parts royalsocietypublishing.org/journal/rsos R. Soc. Open Sci. ...
... Furthermore, prehistoric Varanus fossils tend to be rare elsewhere, even on islands where they are native or have been in the past [64,65], so the absence or rarity of fossils cannot be viewed as definitive evidence of absence of these lizards. A more sceptical view of the role of human introduction of Varanus in Micronesia was taken by Crombie & Pregill [3]-who argued that Palauan and Marianan populations were probably not the same species and that the former may be nativeand by Cota [14], who thought that Marianan populations were native or possibly introduced by Chamorros prior to colonization by Western and Japanese powers. ...
In the light of recent phylogenetic studies, we re-assess the
taxonomy and biogeography of the Varanus populations
distributed in the Micronesian islands of Palau, the Western
Carolines and the Marianas. Whether these populations are of
natural origin or human introductions has long been
contentious, but no study has fully resolved that question.
Here, we present molecular and morphological evidence that
monitor lizards of the Varanus indicus Group reached both
Palau and the Mariana Islands sometime in the late Pleistocene
and subsequently differentiated into two separate species
endemic to each geographical region. One species is confined
to the Mariana Islands, and for these populations, we
revalidate the name V. tsukamotoi Kishida, 1929. The other
species has a disjunct distribution in Palau, the Western
Carolines and Sarigan Island in the Northern Marianas and is
herein described as V. bennetti sp. nov. Both species are most
closely allied to each other, V. lirungensis and V. rainerguentheri,
suggesting that colonization of Micronesia took place from the
Moluccas. We discuss the biogeographic distributions of both
species in the light of the likely colonization mechanism and
previous arguments for human introduction, and we argue that
bounties for Palauan populations are ill-advised and plans for
eradication of some other populations must first demonstrate
that they are, in fact, introduced and not native.
... In India, goannas are protected because they eat crabs that plague rice paddy dykes (Greer 1989). On some Pacific islands mangrove monitors (Varanus indicus) regulate populations of polynesian rats (Rattus exulans) and some beetles (Uchida 1967, Cota 2008). More locally, Rosenberg's goannas were reportedly introduced to Reevesby Island in Spencer Gulf to reduce the number of snakes (Mirtschin 1982, Robinson et al. 1985. ...
... Goannas can also influence mammal and insect populations. On the Marshall and Palau islands Mangrove monitors (Varanus indicus) were considered a nuisance and cane toads were introduced to control their numbers (Dryden 1965, Uchida 1967, Cota 2008. Following the decline in mangrove monitors, Polynesian rats increased, and the numbers of beetles that harm coconuts also rose (Uchida 1967, Cota 2008. ...
... On the Marshall and Palau islands Mangrove monitors (Varanus indicus) were considered a nuisance and cane toads were introduced to control their numbers (Dryden 1965, Uchida 1967, Cota 2008. Following the decline in mangrove monitors, Polynesian rats increased, and the numbers of beetles that harm coconuts also rose (Uchida 1967, Cota 2008. Predation by the arboreal lace goanna (V. ...
... These two populations form a well-supported clade that diverged from other members of the V. indicus Group an estimated 1-2 Mya, and from each other several hundred thousand years ago. This pattern supports the long presence of V. indicus s.l. in the region and is consistent with natural colonization of those islands rather than human-mitigated introductions (as has often been proposed, see review by: Cota, 2008). Future detailed sampling in Micronesia could confirm whether all populations are natural or if humans are responsible for some of the populations across these islands, as seems likely for at least those populations in the Caroline and Marshall Islands (Crombie & Pregill, 1999;Kraus, 2009). ...
We provide a geographically well-sampled, time-calibrated molecular phylogeny for the Pacific monitor lizards (Varanus: subgenus Euprepiosaurus) based on ND4 and 16S rRNA mitochondrial DNA sequences. Three well-supported clades, or species groups, are retrieved: the Varanus doreanus Group, the V. jobiensis Group and the V. indicus Group. The subgenus is estimated to have originated in the Mid-Miocene, but extant lineage diversification dates from the Late Miocene and Pliocene. A rapid and widespread radiation of the V. indicus Group into the SouthWest Pacific islands has occurred in the Pleistocene, but colonization onto these islands did not occur in a linear, stepping-stone fashion. Genetically distinct populations-by tradition classified as V. indicus, but seemingly representing distinct species-occur scattered on Tanimbar, several of the Solomon Islands, the Admiralty Islands, the Louisiade Archipelago, Palau and Guam. Our analyses indicate that Varanus jobiensis is a species complex with several divergent lineages that started to separate in the Pliocene and continued in the Pleistocene, the former coinciding with the uplift of the Central Dividing Range on New Guinea. We find that sympatry among species of Euprepiosaurus has not occurred until divergence times of 4.7-5.8 Myr have accrued.
... While the Japanese had introduced the lizard to other islands in the Pacific as biological pest control (pers. comm., T. Hall), evidence suggest this was not the case in the Marianas and that the species either arrived by natural dispersal or was introduced prior to Western or Japanese presence in the archipelago(Cota 2008).Pregill and Steadman (2009) assert that monitor lizards were introduced to Guam no later than 1600. Local residents and government officials in Palau, however, insist the species is recently introduced and invasive in the archipelago, but science suggests that they are more likely native to the islands(Crombie & Pregill 1999; pers. ...
Climate change has been a subject of numerous studies. While findings suggest that most biological taxa will be affected by its manifestations, aspects of a species life history may increase its susceptibility to climate change. Given their reliance on environmental sources of heat to incubate their eggs, I examined the vulnerability to climate change of the avian family Megapodiidae. I also assessed habitat use, susceptibility to sea level rise, and the effect of introduced rats and tourist presence, as added stressors to climate change, on the Micronesian Megapode (Megapodius laperouse senex) in Palau.
Based on available literature, I employed a trait-based assessment to investigate the vulnerability of 21 species of megapodes to climate change. All species were predicted to experience at least a 2°C increase in mean annual temperature, 12 may experience a moderate or greater fluctuation in rainfall, and 16 would be exposed to rising seas. While the most vulnerable megapodes are intrinsically rare and range restricted, mound nesting species may be more resilient to climate change than others.
I examined breeding and foraging habitat use by the mound nesting megapode in the Rock Islands Southern Lagoon Conservation Area (RISL), where it almost exclusively uses low-lying littoral strand habitat for breeding. Megapodes preferentially selected sites that were 1) relatively close to shore, 2) contained large trees, and 3) exhibited greater canopy heights than the surrounding forest. The subspecies foraged in a non-preferential manner and used all littoral habitat with no apparent influence of dominant plant species composition.
Using GIS and the latest spatial data, I modelled the effect of three currently accepted scenarios (0.52 m, 0.98 m, and 1.9 m) of sea level rise on their known breeding habitat. The RISL is comprised of 3,857.5 ha of forested cover of which megapodes used 120.8 ha (3.1%) for breeding, with an additional 25.3 ha potentially available to them. Megapodes may lose at least 32.5% to 43.3% of known breeding habitat and 25.7% to 31.3% of potential habitat to inundation, respectively.
Using passive chew-tag and call playback surveys, I examined whether introduced rats and tourist presence may negatively affect megapodes in the RISL. Rat detection probability and site occupancy were significantly higher on tourist visited (89% and 99%, respectively) compared to tourist-free islands (52% and 73%). I detected significantly more megapodes at stations on tourist-free islands (93%) than tourist visited (47%), but relative abundance was not significantly different between island types. My findings suggested no significant relationship between rats and megapodes, a negative relationship between tourist presence and megapodes, and augmentation of rat populations by tourist presence.
I compared the ecology of, and IUCN listed threats for, Micronesian Megapodes in Palau with those in the Mariana Islands. I proposed both the inclusion of an additional climate change related threat based on my sea level rise modelling, and new ranking of all IUCN threats by subspecies. Lastly, I proposed research and data acquisition priorities necessary to fill current gaps in the knowledge of megapodes in Palau and facilitate its long-term conservation.
... Rats (Rattus spp.) and Black Drongos (Dicrurus macrocercus) have been introduced (Baker 1951, Steadman 1999. Mangrove monitor lizards (Varanus indicus) also occur on Rota, although the origin of the population is debated (Steadman 1999, Cota 2008, Pregill and Steadman 2009). Monitor lizards do not appear to be important nestling stage predators on Rota (Table 1). ...
Comparative studies of nest predation and identification of nest predators promote understanding of the selective environment that shapes avian life histories. Due to the low diversity of native mammalian and reptilian predators on oceanic islands, insular forest birds are assumed to incur lower nest predation rates than related continental species. We studied correlates of nest predation in insular and continental subspecies of Rufous Fantail (Rhipidura rufifrons) found on the island of Rota and in eastern Australia. Overall, daily survival rate (DSR) was similar between study sites, but egg stage DSR (laying and incubation) was higher in Australia than on Rota while nestling stage DSR was higher on Rota than in Australia. DSR was negatively related to nest age in Australia and the magnitude of this relationship varied by year. On Rota, DSR was higher in the nestling stage than during the egg stage and also higher on our study plot where Mariana Crows (Corvus kubaryi)-the principal nest predator-were less common. Although climate variables did not predict DSR at either site, in Australia, lace monitors (Varanus varius) were more likely to prey upon nests on days without rain. Lace monitors also tended to prey upon nests late in the nestling stage, which likely contributed to the decline of DSR with age. Our results suggest that life history variation between continental and insular birds may be explained, in part, by differences in age-dependent DSR due to the reduced diversity of certain predator guilds on oceanic islands. Therefore, consideration of the nest predator community and age-dependent nest predation risk could help explain additional life history variation in comparative studies.
... Monitor lizards (family Varanidae) are distributed over most of Africa and Australia, through India, Ceylon, Malaysia, and into the islands of the equatorial Western Paciic. The Mangrove Monitor (Varanus indicus) is a large lizard, reaching 1.5 m in total length on Guam, with a range encompassing extreme northeastern Australia, New Guinea, and the Solomon, Palau, Caroline, Marshall, and Mariana Islands (Cota, 2008). They are found on all major island groups of Mi- cronesia, but their method and time of distribution is not known. ...
The restoration of the Habitat Management Unit (HMU) on Naval Support Activity Andersen (NSAA) aims to effect ecosystem restoration through the removal and exclusion of introduced species and the re-establishment and propagation of native species, with focus on the reintroduction of native forest bird species and focused management for federally listed and other sensitive species.
