A counterintuitive climate tale of knock-on effects due to hotter, dryer conditions
Benjamin Rey/Wits University
When nocturnal aardvarks start sunbathing, something’s wrong.
If the animals are desperate enough to bask like some cold, sluggish turtle, it’s because they’ve got the chills. Robyn Hetem, an ecophysiologist, has the body temperature data to prove it — collected from late 2012 into 2013, the hottest summer the arid Kalahari region in South Africa had seen in more than 30 years.
Hotter, drier conditions are predicted to become the norm for southern Africa as the climate changes. Now Hetem and colleagues have used that foretaste of change to show that higher temperatures might hammer the normally heat-tolerant aardvarks by shrinking the animals’ food supply.
Aardvarks live their burrow-digging lives just about anywhere in sub-Saharan Africa except the desert. The toothless night-foragers dine by slurping insect colonies. One of Hetem’s students at the University of the Witwatersrand in Johannesburg spent two years collecting hundreds of aardvark droppings and can confirm that Orycteropus afer in the Kalahari eat only termites and ants. Yet the solitary, long-snouted, knee-high mammals are more closely related to elephants than to any pointy-nosed South American anteater.
An aardvark looks “very lethargic but is incredibly strong and fast,” Hetem says. The researchers wanted to fit wild aardvarks with tracking devices and data loggers but first had to catch the animals. Nets failed. Traps failed. One cornered aardvark burst out of a burrow, knocked four men to the ground and then outran them.
Eventually, researchers placed instruments on six animals. When the Kalahari baked and good rains were months late, the aardvarks grew thin and bony. They started hunting during the day and sunbathing. The animals, once able to internally stabilize their body temperatures, started to have great plunging chills at night, according to data loggers. That’s a sign of starvation, Hetem says, and occurs when the body no longer has energy to warm itself. Five of the six tracked animals died, along with at least 11 other aardvarks in the neighborhood.
Aardvark heat tolerance wasn’t the problem. The animals were dying off because their food couldn’t take the heat and drought, Hetem and colleagues argue in the July Biology Letters. Hot, dry spells can make ant and termite colonies shrink and retreat to hard-to-reach hideouts.
Other African wildlife might suffer from a shortage of aardvarks, which are prodigious burrow diggers. In a Kalahari study, one aardvark used more than 100 burrows in two years. So many hideaways are a boon for others. Bat-eared foxes, warthogs, birds called ant-eating chats and at least two dozen other species pop into aardvark architecture, sometimes outright moving in. If aardvarks dwindle, shelter might grow scarcer for other animals.
“We kind of think of climate change as: Things are going to get hotter and species might be sensitive to it,” Hetem says. “There’s so much more we need to understand.”
B. Rey et al. Drought-induced starvation of aardvarks in the Kalahari: an indirect effect of climate change. Biology Letters. Vol. 13, July 2017. doi: 10.1098/rsbl.2017.0301.
G.M. Whittington-Jones, R.T.F. Bernard and D.M. Parker. Aardvark burrows: a potential resource for animals in arid and semi-arid environments. African Zoology. Vol. 46, October 2011, p. 362. doi: 10.3377/004.046.0215.
S. Milius. Ways to beat heat have hidden costs for birds. Science News. Vol. 190, September 17, 2016, p. 15.