Climate change and decreasing snakes population

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Climate change is affecting many animals, and the main focus has been put on arctic animals, such as polar bears. However, did you know that many herpetofauna populations are also greatly affected by the change in temperature are the globe (Reading et al. 2010)? Harlequin Frog and Golden Toad have been reported extinct globally due to climate warming (Pounds and Crump 1994). As mentioned in the importance of unattractive snakes, Aubret and Shine (2009) demonstrated the lack of plasticity in adult snakes to deal with yearly variation of temperature. They (2009) showed reduced growth rate in thermally challenged young snakes, which could lead to late sexual maturity and lower reproductive success (Brown and Shine 2007), and lower ingestible prey sizes and limit prey choices (King 2002). The effects of climate change on animals are often hard to assess because species demonstrate varied adaptation, dispersal abilities, phenotypic plasticity and thermal tolerance (Groom et al. 2006). Also, scientists have to consider the inter-individual variation in responses to the change in temperature (Groom et al. 2006).

Temperature effects

The main abiotic consequences of climate change on snakes would be the change in temperature, warming and cooling of the planet. A stable ambient temperature is critical to ectothermic snakes which rely on thermoregulation to maintain body temperatures. In North America particularly, Weatherhead et al. (2012) addressed the ability of black ratsnakes (Elaphe obsoleta) to behaviourally modify their thermoregulatory strategy in response to different environmental temperature corresponding to latitudinal variation. Black ratsnakes adjusted the duration of their active season to cope with the temperature variation (Blouin-Demers et al. 2002; Weatherhead et al. 2012). This might reduce their fitness because adjusted thermoregulatory tactics could be energetically costly (Weatherhead et al. 2012). The brevity of active season in Ontario black ratsnakes has been associated with slower growth rate and later sexual maturation, making the population fragile to population decline (Blouin-Demers et al. 2002).

Although the effects of climate change on snakes population structure still remain unknown, various physiologically based processes, such as juvenile development, sexual maturation, and locomotion, would be strongly dependent of the ambient temperature (Brown and Weatherhead 2000). This would be especially true for species living at high altitudes and latitudes because of the greater seasonal variation of temperature. Brown and Weatherhead (2000) found that the reproductive success of female northern water snakes (Nerodia sipedon) was largely dependent on the climatic conditions; because ambient temperature variation could affect body size and rate of sexual maturation. Human-induced climate change is accelerating the extinction of many snakes species due to the incapability of these species to cope with temperature variation.

Precipitation effects

Another change facilitated by climate change is the change in precipitation, causing some area to be drier (leading to droughts), and others becoming wetter (flooding potentially) (Groom et al. 2006). Shine (1991) recorded a drought event in Australia which led to great decline of common blacksnakes population because of the decrease of food (frogs) abundance. This is due to the fact that most amphibians are restricted to wetland or moist area to maintain moisture of their skin. Droughts cause decrease moist habitats for amphibians, and hence reduce food availability of many other species, including birds and snakes (Shine 1991) .

References:

Aubret, D., and R. Shine. (2009). Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms? The Journal of Experimental Biology 213: 242-248.

Blouin-Demers, G., K. A. Prior., and P. J. Weatherhead. (2002). Comparative demography of black rat snakes (Elaphe obsoleta) in Ontario and Maryland. J. Zool., Lond. 256: 1-10.

Brown, G. P., and P. J. Weatherhead. (2000). Thermal ecology and sexual size dimorphism in northern water snakes, Nerodia sipedon. Ecological Monographs 70(2): 311-330.

Brown, G. P. and R. Shine. (2007). Rain, prey and predators, climatically driven shifts in frog abundance modify reproductive allometry in a tropical snake. Oecologia 154: 361-368.

Groom, M. J., G. K. Meffe., and C. R. Carroll. Principles of Conservation Biology, Third Edition. Sunderland, Massachusetts: Sinauer Associates, Inc, 2006. Print.

King, R. B. (2002). Predicted and observed maximum prey size-snake size allometry. Functional Ecology 16: 766-772.

Pounds, A., and M. L. Crump. (1994). Amphibian declines and climate disturbance: the case of the golden toad and the harlequin frog. Society for Conservation Biology 8(1): 72-85.

Reading, C. J., L. M. Luiselli, G. C. Akani, X. Bonnet, G. Amori, J. M. Ballouard, E. Filippi, G. Naulleau, D. Pearson and L. Rugiero. (2010). Are snake populations in widespread decline? Biology Letters doi:10.1098.

Shine R. 1991. Australian Snakes: A Natural History. Ithaca (NY): Cornell University Press.

Weatherhead, P. J., J. H. Sperry., G. L. F. Carfagno., G. Blouin-Demers. (2012). Latitudinal variation in thermal ecology of North American ratsnakes and its implications for the effect of climate warming on snakes. Journal of Thermal Biology 37: 273-281.