Threatened: Mountain gorillas will come under increasing stress as global temperatures increase. Photo: Robert Haasmann
As temperatures rise, the world’s endangered mountain gorillas are increasing the frequency that they drink water, new research has found.
Mountain gorillas rarely drink water and obtain sufficient quantities of it from the vegetation they eat. But increasing temperatures will make them more reliant on streams, rivers, puddles or swamps to regulate their body temperatures and avoid dehydration. And because they live at higher elevations, they are also more susceptible to faster temperature rises.
The researchers’ findings suggest climate change is affecting their behaviour and could pose unexpected negative consequences for their conservation and overall survival, according to the team of researchers behind the study.
Only about 1 000 individual mountain gorillas exist in two small isolated mountain top islands in the Virunga volcanic mountains that border Rwanda, Uganda and the Democratic Republic of the Congo and in the Bwindi Impenetrable National Park in Uganda.
The researchers examined the water drinking behaviour of two mountain gorilla populations between 2010 and 2020 in Virunga and Bwindi, and found that both populations showed an increase in water drinking at higher average temperatures than at cooler ones.
“Mountain gorillas drink water more often as the temperature increases,” said Edward Wright, of the Max Planck Institute for Evolutionary Anthropology, and an author of the study. “In these conditions, drinking water likely helps to maintain a healthy body temperature range.”
Understanding how animals obtain water is increasingly important in the face of climate change, as warmer temperatures and more extreme weather conditions are predicted to influence water availability, which could have implications for how they use their limited habitat, he said. “This is particularly important in endangered species which are vulnerable to extinction, such as mountain gorillas.”
A greater reliance on free-standing water has several effects on the survival of these fragile primate populations including more parasite and human disease exposure. And, because mountain gorillas are a small, isolated species with a limited habitat range, water is not always guaranteed in the home range of each group.
According to the study, the slow life history of mountain gorillas limits their ability to evolve adaptations that are better suited to new climatic conditions fast enough to mitigate the detrimental effects of climate change.
“Mountain gorillas are also geographically highly restricted due to intense human pressure surrounding their current habitat, such that they cannot disperse to other areas.”
The study’s results indicate that mountain gorillas “may have to work harder to maintain water balance in the future, given that temperature and the duration of dry spells are expected to increase”.
Both Uganda and Rwanda are already experiencing the effects of climate change with increasing temperatures and frequencies of extreme weather events, according to the study. Mean annual temperature increases of about 2.1°C have been recorded over the past 50 years.
“Future projections indicate that this trend is likely to continue, with increases of 1°C to 2.5°C between 2000 and 2050. Furthermore, rainfall has become less seasonal, with both an increase in rainfall over time and increases in the duration of dry spells, trends that are likely to continue in the future.”
The authors describe how a considerable proportion of primate species are predicted to be vulnerable to drought. “Moreover, primate habitats are predicted to experience 10% more warming than the global mean increase in temperature, with 86% of primate species likely to experience increases of over 3°C in maximum temperatures by 2050.”
Higher elevation regions are also experiencing faster increases in temperature than lower elevation ones. “Given the vulnerability of primates to dry spells, it is vital to look for indicators of physiological stress in endangered species, such as changes in the occurrence of water drinking caused by climate change.”
Undoubtedly, the authors say, the direct effect of climate change is likely to be a bigger problem for species living in more arid environments that face reduced access to sufficient quantities of either free-standing sources of water or preformed water.
“However, this study emphasises that climate change may have negative consequences even for rainforest dwelling mammals that routinely obtain nearly all of their water from dietary [sources]. This may be especially true for endangered species in small isolated populations, which are vulnerable to drought and the risk of extinction.”
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