Tuesday, August 30, 2011

The Impact of Climate Change on Four Species of Snakes

Bitis nasicornis. JCM

The prediction that climate change will have dramatic impacts on organisms has been discussed for a while. Three new studies support the idea that climate change will greatly influence snakes and how they will adjust to changes in habitat, competitor abundance and changes in the available food supply. These changes are occurring now and will continue into the future. 

Pierluigi Bombi and colleagues have two papers (Bombi et al. 2011a,b). In the first they report (Bombia 2011a) that the most endangered snake in Italy, the Sardinian Whipsnake, Hemorrhois (= Coluber) hippocrepis, is threatened by human alteration of its habitat and suggest that this is exacerbated by climate change. In Italy, the species in known only from the southern end of Sardinia. While nothing is known about the potential effects climate change could exert on this species, ecological modeling of its habitat suggested climate changes will greatly alter the snake's remaining habitat. Changing climate conditions will cause a dramatic reduction of suitable habitat by 2020, with a further collapse by 2050 (down to 11 km2). They found only one existing protected area will likely retain suitable habitats for this species.

In a second article, Bombi et al. (2011b) used data collected over the past 15 years on the ecology and population abundance of the Gaboon viper (Bitis gabonica) and the Nose-horned Viper (Bitis nasicornis) in southern Nigeria. The field work found several high-abundance and low-abundance populations of these two species. The authors analyzed the potential effects of climate change by modeling the current dataset on viper abundance (both high and low) using generalized additive models. Using climatic surfaces of current conditions as spatially explicit predictors, they projected viper abundance into a future climatic scenario. The future climatic conditions seemed appropriate for the success of the climatic niche used by the high-abundance Gaboon viper in their study area. While the future climatic niche for the high-abundance nose-horned viper populations was predicted narrow. In future scenarios, the two species were predicted to have a larger overlap in their climatic niche, and this is likely to increase interspecific competition.

Beata Ujvari at the University of Wollongon and colleagues (2011) note that climate change can result in the movement of resources critical for the viability of a population, and a species' resilience to such changes will depend upon its ability to shift its activities away from no-longer-suitable sites to exploit new opportunities. Common sense would suggest that predators should be able to track spatial shifts in prey availability, but data on water pythons (Liasis fuscus) in tropical Australia suggest a less encouraging scenario. Water Pythons undergo seasonal migrations that may cause them to move up to 10 km, following flooding-induced migrations by their prey, the Native Dusky Rats (Rattus colletti). However, when an extreme flooding event virtually eliminated the rats for three years, the local pythons did not disperse despite the presence of abundant rats only 8 km away; instead, many pythons starved to death. This inflexibility suggests species that track seasonally migrating prey may do so by responding to habitat attributes that have consistently predicted prey availability over evolutionary time, rather than reacting to proximate cues that signal the presence of prey per se. Therefore, a species' vulnerability to climate change will be increased by an inability to shift its activities away from historical sites toward newly favorable areas.


Bombi, P.and Capula, M., Amen, M and Luiselli, L.. 2011a.Climate change threatens the survival of highly endangered Sardinian populations of the snake Hemorrhois hippocrepis. Animal Biology 61:239-248.
Bombi, P., Akani, G. C., Ebere, N., Luiselli, L. 2011b. Potential effects of climate change on high- and low-abundance populations of the Gaboon viper (Bitis gabonica) and the nose-horned viper (B. nasicornis) in southern Nigeria. The Herpetological Journal 21:59-64.

Ujvari, B., Shine, R., Madsen, T.. 2011. How well do predators adjust to climate-mediated shifts in prey distribution? A study on Australian water pythons. Ecology 92:777–783. [doi:10.1890/10-1471.1]

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