As temperatures rise on the savannas of East Africa, large herbivores like giraffes need to adapt. This they have done fairly well in the Tarangire region of Tanzania, according to a decades-long study by scientists from the University of Zurich and Pennsylvania State University.
The researchers observed nearly 2,500 giraffes over more than 1,000 square kilometers both inside and outside protected areas, analysing the effects of temperature, rainfall and vegetation on local giraffes during Tanzania’s short rains, long rains and dry season.
“Studying the effects of climate and human pressures on a long-lived and slow-breeding animal like a giraffe requires monitoring their populations over a lengthy time period and over a large area, enough to capture both climate variation and any immediate or delayed effects on survival,” explains Monica Bond, a postdoctoral research associate in the Department of Evolutionary Biology and Environmental Studies at the University of Zurich,
In all, the scientists kept track of 2,385 giraffes of all ages over the final eight years of the two-decade study period. The scientists paid especial attention to how a changing climate and human activities affected the herbivores.
“Contrary to expectations, higher temperatures were found to positively affect adult giraffe survival, while rainier wet seasons negatively impacted adult and calf survival,” they report.
Rather than overheat because of their large bodies in rising temperatures, adult giraffes fared surprisingly well, thanks to their anatomy.
“The giraffe has several physical features that help it to keep cool, like a long neck and legs for evaporative heat loss, specialized nasal cavities, an intricate network of arteries that supply blood to the brain, and spot patches which radiate heat,” says Derek Lee, an associate research professor of biology at Pennsylvania State University and senior author of the study.
However, the expert warns, “temperatures during our study period may not have exceeded the tolerable thermal range for giraffes, and an extreme heat wave in the future might reveal a threshold above which these massive animals might be harmed.”
During heavier rains more adult and juvenile giraffes succumbed probably as a result of parasites and diseases such as Rift Valley fever virus and anthrax. Human activities also had an overall negative impact.
“Giraffes living near the peripheries of the protected areas are most vulnerable during heavy short rains,” says Arpat Ozgul, a professor at the University of Zurich. “These conditions likely heighten disease risks associated with livestock, and muddy terrain hampers anti-poaching patrols, leading to increased threats to giraffe survival.”
Further changes in the climate of East Africa, such as heavier rainfalls during the short rains season, will likely place greater stresses on local giraffes, pushing them closer to extinction, the scientists argue.
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