Detailed biological data are informative, but robust trends are needed for informing sustainability of wildlife harvesting: A case study of reptile offtake in Southeast Asia

Natusch, Daniel J. D.; Lyons, Jessica A.; Riyanto, Awal; Mumpuni, _; Khadiejah, Syarifah; Shine, Richard

doi:10.1016/j.biocon.2019.02.016

Cited by 24 publications

(35 citation statements)

References 31 publications

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“…Python growth in our study was also associated with their sex. While we cannot discount the possibility of sex differences in growth being driven by sex differences in food intake, we suggest this is unlikely and note that our results are consistent with the known sexual size dimorphism in this species, and closely related species ( Natusch & Lyons, 2014 ; Natusch et al, 2019 ). Our results contradict the notion that pythons do not diverge in size until post sexual maturity ( Natusch & Lyons, 2014 ).…”

Section: Discussionsupporting

confidence: 70%

“…Yet, for closely related species, such as the reticulated python ( Python reticulatus ) large numbers of individuals are harvested from the wild. While the large annual harvest of these wild, large-bodied reptiles is thought to be sustainable, captive-bred animals are often favoured by the high-end leather industry based on the perception that captive-bred pythons have higher sustainability and animal welfare credentials ( Natusch & Lyons, 2014 ; Natusch et al, 2019 ; Natusch et al, 2016 ). However, concerns have been raised that snakes marketed as captive-bred may, in fact, be wild-caught, and laundered through captive-breeding facilities under the guise of being captive-bred ( Kasterine et al, 2012 ).…”

Section: Introductionmentioning

confidence: 99%

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The impact of PIT tags on the growth and survival of pythons is insignificant in randomised controlled trial

Taggart

Morris

Caraguel

2021

PeerJ

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Individual identification is fundamental to the study of captive and wild animals but can have adverse impacts if the method of identification is inappropriate for the species or question of interest. We conducted a randomised controlled trial to test whether passive integrated transponder (PIT) tags reduced the growth or survival of pythons. We randomly allocated 200 captive-bred Burmese python (Python bivittatus) hatchlings into two groups, tagged versus untagged. Hatchlings were individually identified using a combination of PIT tags and unique colour patterns, and their mass, snout-vent length (SVL) and body condition measured at 9, 73, 134, 220, 292 and 385 days of age. We recorded the date of all mortalities. Python morphometrics and their rate of change increased or fluctuated non-linearly with age. The impact of PIT tagging on python body mass and body mass growth over the 376 day study period was insignificant. PIT tagging additionally had an insignificant impact on python survival. However, we found minor differences in SVL growth between tagged and untagged pythons. These differences peaked at approximately 0.5 mm/day and appeared to drive similar, but more pronounced, differences between tagged and untagged pythons in their rate of change in body condition; peaking at approximately 3–4 g/day. While we cannot be certain that these small differences are, or are not, biologically meaningful, they nonetheless appear to be short-term and readily resolved. Unsurprisingly, the strongest driver of python growth was their age, with growth rapidly increasing or highest amongst younger snakes for all measures of size. Python sex was associated with their body mass and survival, with higher mass but lower survival amongst females. Python size at hatching did not impact on their growth or survival. Our results confirm that PIT tags are a valuable and effective tool for the identification and tracking of captive pythons, and snakes generally, and meet high safety and animal welfare standards.

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Section: Discussionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

The impact of PIT tags on the growth and survival of pythons is insignificant in randomised controlled trial

Taggart

Morris

Caraguel

2021

PeerJ

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“…reticulatus and V . salvator are legally collected from the wild by licensed hunters and brought to abattoirs for processing [ 13 , 14 ]. Animals are kept alive at the facility for up to a week before being killed using a strong blow to the head followed by decapitation.…”

Section: Methodsmentioning

confidence: 99%

“…In May 2019, we examined responses to CO 2 in these reptiles in Malaysia (2˚14'N, 1030 3'E) and Thailand (17˚38'N, 100˚07'E) at two commercial facilities producing meat for human consumption and skins for the exotic leather trade. In Malaysia, free-roaming M. reticulatus and V. salvator are legally collected from the wild by licensed hunters and brought to abattoirs for processing [13,14]. Animals are kept alive at the facility for up to a week before being killed using a strong blow to the head followed by decapitation.…”

Section: Study Species and Locationsmentioning

confidence: 99%

Behavioral and corticosterone responses to carbon dioxide exposure in reptiles

Natusch

Aust

Khadiejah³

et al. 2020

PLoS ONE

Self Cite

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The use of carbon dioxide (CO 2) exposure as a means of animal euthanasia has received considerable attention in mammals and birds but remains virtually untested in reptiles. We measured the behavioral responses of four squamate reptile species (Homalopsis buccata, Malayopython reticulatus, Python bivitattus, and Varanus salvator) to exposure to 99.5% CO 2 for durations of 15, 30, or 90 minutes. We also examined alterations in plasma corticosterone levels of M. reticulatus and V. salvator before and after 15 minutes of CO 2 exposure relative to control individuals. The four reptile taxa showed consistent behavioral responses to CO 2 exposure characterized by gaping and minor movements. The time taken to lose responsiveness to stimuli and cessation of movements varied between 240-4260 seconds (4-71 minutes), with considerable intra-and inter-specific variation. Duration of CO 2 exposure influenced the likelihood of recovery, which also varied among species (e.g., from 0-100% recovery after 30-min exposure). Plasma corticosterone concentrations increased after CO 2 exposure in both V. salvator (18%) and M. reticulatus (14%), but only significantly in the former species. Based on our results, CO 2 appears to be a mild stressor for reptiles, but the relatively minor responses to CO 2 suggest it may not cause considerable distress or pain. However, our results are preliminary, and further testing is required to understand optimal CO 2 delivery mechanisms and interspecific responses to CO 2 exposure before endorsing this method for reptile euthanasia.

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“…Earlier studies on the species’ populations focused on determining the differences on abundance between natural forest and human-modified habitats using either distance surveys [ 9 , 11 ] or mark-recapture methods [ 19 , 20 ]. However, more detailed information is needed to properly evaluate the status of a population, especially when focusing on species that are target for either commercial or subsistence consumption [ 20 , 25 , 26 ]. Hence, survival and recruitment estimations, as well as body size distribution become fundamental parameters not only to accurately estimate extraction rates for commercial purposes, but also to assess the impact of landscape fragmentation on the health of the population.…”

Section: Introductionmentioning

confidence: 99%

The critical role of natural forest as refugium for generalist species in oil palm-dominated landscapes

et al. 2021

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In Borneo, oil palm plantations have replaced much of natural resources, where generalist species tend to be the principal beneficiaries, due to the abundant food provided by oil palm plantations. Here, we analyse the distribution of the Asian water monitor lizard (Varanus salvator) population within an oil palm-dominated landscape in the Kinabatangan floodplain, Malaysian Borneo. By using mark-recapture methods we estimated its population size, survival, and growth in forest and plantation habitats. We compared body measurements (i.e. body weight and body length) of individuals living in forest and oil palm habitats as proxy for the population’s health status, and used general least squares estimation models to evaluate its response to highly fragmented landscapes in the absence of intensive hunting pressures. Contrary to previous studies, the abundance of lizards was higher in the forest than in oil palm plantations. Recruitment rates were also higher in the forest, suggesting that these areas may function as a source of new individuals into the landscape. While there were no morphometric differences among plantation sites, we found significant differences among forested areas, where larger lizards were found inhabiting forest adjacent to oil palm plantations. Although abundant in food resources, the limited availability of refugia in oil palm plantations may intensify intra-specific encounters and competition, altering the body size distribution in plantation populations, contrary to what happens in the forest. We conclude that large patches of forest, around and within oil palm plantations, are essential for the dynamics of the monitor lizard population in the Kinabatangan floodplain, as well as a potential source of individuals to the landscape. We recommend assessing this effect in other generalist species, as well as the impact on the prey communities, especially to reinforce the establishment of buffer zones and corridors as a conservation strategy within plantations.

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Detailed biological data are informative, but robust trends are needed for informing sustainability of wildlife harvesting: A case study of reptile offtake in Southeast Asia

Cited by 24 publications

References 31 publications

The impact of PIT tags on the growth and survival of pythons is insignificant in randomised controlled trial

The impact of PIT tags on the growth and survival of pythons is insignificant in randomised controlled trial

Behavioral and corticosterone responses to carbon dioxide exposure in reptiles

The critical role of natural forest as refugium for generalist species in oil palm-dominated landscapes

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