Escape in the Serengeti: Hyraxes have become accustomed to increasing human disturbances
Featured image: Rock Hyrax in their typical rock outcrops kopjes near a building (photo by Regina Hart -flickr.com
Mbise FP, Fredriksen KE, Ranke PS, Jackson C, Fyumagwa R, Holmern T, Fossøy F, Røskaft E. 2019. Human habituation reduces hyrax flight initiation distance in Serengeti. Ethology. doi:10.1111/eth.12968.
Eco-tourism: is no haven safe?
It’s well documented that human population and urban development are projected to increase, which will result in major habitat loss and increasing impacts for many species. Many species are intolerant of humans and have to disperse when human settlements become too dense near their home ranges. One way in which we can protect wildlife is through the designation of National Parks or Reserves where many kinds of development and permanent settlements are forbidden. However, ecotourism can still bring a great deal of human disturbance through high levels of activity, permitted use of motor vehicles, hiking and camping grounds. Because of this, Franco Mbise (University of Dodoma, Conservation Biology) and his team decided to study whether two species of hyraxes (figure 1) are being disturbed by the presence of humans in the Serengeti. Hyraxes are small herbivorous mammals that grow up to 2 feet long . The Serengeti National Park is home to many species of African wildlife and also has a variety of accommodations for humans such as campgrounds and luxury lodges. This park receives as many as 350,000 visitors per year.
Figure 1: Collage of the two species of hyraxes. First photo shows the Rock hyrax (Procavia capensis; image by Angoria -Wikimedia commons) seen in the typical rock outcrops they live in called kopjes. The second photo shows the Bush hyrax (Heterohyrax bruceii; image by JaySef -Wikimedia commons).
Measuring fear: when should animals flee
When animal populations are constantly disturbed they either disperse to areas with less disturbance or become tolerant to the disturbance over time. The reason this happens is because if animals react to constant disturbance then it becomes energetically costly to flee. Constantly running and hiding is tiring and the animals may have to abandon food or mates. One way in which scientists have traditionally modeled fears is by measuring how close an incoming threat (usually a modeled predator or a human) can approach before an animal escapes. The distance between the approaching threat and the animal when it flees it called flight initiation distance (often shorthanded as FID). Animals that are fearful and intolerant of the type of disturbance approaching are expected to have very long FID distances. In contrast, as animals become less fearful of that threat then FID should decrease so that the animal decrease costs of constantly fleeing.
To study whether human exposure affected the fear responses in hyraxes, Franco Mbise and his team studied 43 kopjes within the Serengeti National Park. Some of these kopjes were very close to human buildings (see feature image). If hyraxes living in close proximity to humans have modulated their escape response, then FID should be shorter than the populations in kopjes less disburbed by humans. That was, in fact, the finding that researchers discovered. The researchers observed that hyraxes near human settlements had fleeing distances nearly 4 times less than less disturbed populations (Figure 2).
Figure 2: Flight response of hyraxes in rock outcrops nearby human settlements and in rock outcrops without humans. Hyraxes near human premises had shorted flight initiation distances, suggesting that they are more tolerant of human disturbances. (Figure edited from Franco Mbise et al., 2019). The data are presented in log scale.
Hyraxes hanging out with humans
The findings of this article showed that hyraxes successfully modulate their fear response to the presence of humans. This is good because they are not being displaced by increasing proximity to human settlements. However, not all animals are able to tolerate constant disturbance of human activity. Additionally, when animals become adjusted to humans they may also be more exposed to other facets of human settlements such as human food sources, humans pets and pests associated with these settlements Additionally, some worry that tolerance to humans can also lead to increases in risk-taking behaviors potentially making the animals more vulnerable to their natural predators. If you are planning on visiting wildlife as part of your trip remember that we can have great impact on how we interact with animals. More importantly, make sure you do not feed wildlife and that you leave no trash behind.