Impact of invasive spotted deer (Axis axis) on tropical island lizard communities in the Andaman archipelago

Mohanty, Nitya Prakash; Harikrishnan, S.; Sivakumar, K.; Vasudevan, Karthikeyan

doi:10.1007/s10530-015-1006-0

“…Our study provides new insights into a rarely studied behaviour in lizards, the adaptive significance of sleeping behaviour in predator avoidance and resource partitioning in syntopic and congeneric species. Based on reported negative impacts on lizard population by spotted deer ( Axis axis ), an invasive mammalian herbivore in the Andaman Islands ( Mohanty et al, 2016 ), our findings lend support to the importance of understory vegetation structure for long-term survival of these endemic lizards in the Islands.…”

Section: Discussionsupporting

confidence: 74%

“…The study sites had a tree (>100 mm in GBH) density of ca. 950 ha −1 ( Mohanty et al, 2016 ) which would provide many more perches than smaller plants of narrow girth. The almost exclusive use of narrow girth plants (<100 mm in GBH) by the lizards appears to be more than their availability at the study sites.…”

Section: Discussionmentioning

confidence: 99%

Watch out where you sleep: nocturnal sleeping behaviour of Bay Island lizards

Mohanty

¹

,

Harikrishnan

²

,

Vasudevan

³

2016

PeerJ

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Sleeping exposes lizards to predation. Therefore, sleeping strategies must be directed towards avoiding predation and might vary among syntopic species. We studied sleeping site characteristics of two syntopic, congeneric lizards—the Bay Island forest lizard, Coryphophylax subcristatus and the short-tailed Bay Island lizard, C. brevicaudus and evaluated inter-specific differences. We measured structural, microclimatic and potential predator avoidance at the sleeping perches of 386 C. subcristatus and 185 C. brevicaudus. Contrary to our expectation, we found similar perch use in both species. The lizards appeared to use narrow girth perch plants and accessed perches by moving both vertically and horizontally. Most lizards slept on leaves, with their heads directed towards the potential path of a predator approaching from the plant base. There was no inter-specific competition in the choices of sleeping perches. These choices indicate an anti-predator strategy involving both tactile and visual cues. This study provides insight into a rarely studied behaviour in reptiles and its adaptive significance.

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“…Based on reported negative impacts on lizard population by spotted deer (Axis axis), an invasive mammalian herbivore in the Andaman Islands (Mohanty et al 2016), our findings lend support to the importance of understory vegetation structure for long-term survival of these endemic lizards in the Islands. Percentage of lizards observed sleeping on different substrates with varied orientation with respect to the ground and head direction.…”

Section: Resultssupporting

confidence: 73%

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Supplemental Information 2: Raw Data on Sleeping Behaviour of Coryphophylax Lizards Collected From Andaman Islands

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Sleeping exposes lizards to predation. Therefore, sleeping strategies must be directed towards avoiding predation and might vary among syntopic species. We studied sleeping site characteristics of two syntopic, congeneric lizards -the Bay Island forest lizard, Coryphophylax subcristatus and the short-tailed Bay Island lizard, C. brevicaudus and evaluated inter-specific differences. We measured structural, microclimatic and potential predator avoidance at the sleeping perches of 386 C. subcristatus and 185 C. brevicaudus.Contrary to our expectation, we found similar perch use in both species. The lizards appeared to use narrow girth perch plants and accessed perches by moving both vertically and horizontally. Most lizards slept on leaves, with their heads directed towards the potential path of a predator approaching from the plant base. There was no inter-specific competition in the choices of sleeping perches. These choices indicate an anti-predator strategy involving both tactile and visual cues. This study provides insight into a rarely studied behaviour in reptiles and its adaptive significance. 154 and the head direction (inward, outward or perpendicular) of the lizards. We classified the head 155 direction (Fig. 3) with respect to the trunk when the perching substrate was a branch (e.g., inward 156 = head towards the trunk), with respect to the petiole when the substrate was a leaf (e.g., outward 157 = away from the petiole/plant base; perpendicular = across the leaf axis), and with respect to the 158 ground if the substrate was the trunk (e.g., outward = away from the ground). We measured 159 distance to nearest plant in the escape direction of the individual. The escape direction of an 160 individual was assumed to be between 0 о to 180 о in front of its head (NPM and SH personal 161 observations). The nearest point on the adjacent plant was considered to be on the same plane as 162 or below the lizard. We measured all distances using a measuring tape with 0.1 cm precision. Inter-specific and intra-specific variations 226 We found significant differences in perch characteristics between the two species but effect sizes 227 in all the comparisons were small ( Table 2). The two species showed distinct patterns in the way 228 they accessed perches (Fig.4). While both species moved similar distances vertically, C.229 subcristatus accessed perches away from the trunk (Fig.4). In contrast, C. brevicaudus used 230 perches close to the trunk (Fig.4). We found that vertical distance contributed relatively more to the total distance moved 232 than horizontal distance (Fig.4). After controlling for girth of perch plants, body size positively 237 brevicaudus (R 2 = 0.01, β = -2.13, SE = 1.65, p = 0.19) and had a statistically significant but 238 small effect size in case of C. subcristatus (R 2 = 0.02, r = -0.14, β = -2.1, SE = 0.73, p = 0.004). 239We found no difference between males and females of C. subcristatus with respect to 243 Site fidelity 244 We redetected eight out of the ten marked individuals of C. subc...

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“…The community of lizards that occupy the Andaman & Nicobar Islands is the outcome of processes of natural selection during their evolutionary history. Now, their persistence in these islands is fraught with human-induced habitat loss and biological invasions 71 that will hasten their extinction. With the significant turnover of species in the archipelago (between the Andaman Islands and the Nicobar Islands; within the Nicobar Islands), any attempt to conserve species through protected areas will have to devote equal effort in all the island groups.…”

Section: Discussionmentioning

confidence: 99%

Niche dissociated assembly drives insular lizard community organization

Harikrishnan

¹

,

Vasudevan

²

2018

Sci Rep

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Interspecific competition for resources leading to niche partitioning is considered as one of the major drivers of community assembly. Competitive niche partitioning is diagnosed from species co-occurrence, species abundance distributions (SADs), and body size distributions of species. For several decades, studies have explored these patterns for the relative significance of interspecific competition in shaping communities. We explored these patterns in a finite assemblage of insectivorous lizards in the Andaman & Nicobar Islands, both at the level of archipelago and individual islands. Negative geographic co-occurrences occurred only between species pairs in islands separated by deep ocean channels. Ecologically similar species did not show positive co-occurrence in guild co-occurrence analyses, indicating that the negative geographical co-occurrences between species in islands were due to historical allopatry. Species abundance distribution was best explained by a Pareto distribution in both metacommunity and local communities. There was no predictable spacing of body sizes among co-existing species in local communities. The empirical data on insular lizard community on species co-occurrence, SADs, and body size ratios does not lend support to assortment of species in islands caused by niche subdivision. Such niche-dissociated assembly of species in islands might be an important factor in formation of biological communities, regardless of geographic scale.

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Impact of invasive spotted deer (Axis axis) on tropical island lizard communities in the Andaman archipelago

Cited by 15 publications

References 22 publications

Watch out where you sleep: nocturnal sleeping behaviour of Bay Island lizards

Watch out where you sleep: nocturnal sleeping behaviour of Bay Island lizards

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Niche dissociated assembly drives insular lizard community organization

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