Farms and ranches are rough for wildlife. More land taken up for agriculture or livestock means less land for wild animals. Hungry predators around farms get a double dose of bad news: in addition to being excluded from parts of the landscape, they often get blamed for dead or disappearing livestock. Sometimes farmers and ranchers kill off the predators they suspect to be the culprits. In Botswana, many landowners perceive cheetahs as a major source of livestock loss. But is that perception reasonable, or are cheetahs getting unfairly blamed? Cheetah conservation researcher Lorraine Boast decided to find out.
Privately owned farms and ranches in Botswana tend to be fairly large, and even if subdivided, the paddocks remain quite expansive. That makes carcasses of dead animals hard to find, and when they are found, it’s often too late to identify the most likely cause of death. Smaller animals are often consumed entirely, leaving little evidence behind.
To see if cheetahs are really to blame for such losses, Boast and her colleagues collected cheetah scat from 26 ranches in northwestern Botswana. Some of the ranches kept only livestock like cows, goats, and sheep. Others kept what’s referred to as gamestock: giraffes, zebra, and antelopes. While ranches all use fences, most predators eventually find a way in.
The ranchers identified springbok as the most common species lost to cheetahs, followed by kudu. And they reported losing an average of 23.6 gamestock animals per ranch per year to cheetahs. But the scat told a different story. Cheetahs mostly left springbok alone, and when they did gobble up stock animals, they focused more on waterbuck. The scat revealed that the average ranch in the area could expect to lose fewer than 1.5 cattle and between 2 and 10 gamestock animals each year to wild predators. And because most of the scat came from adult male cheetahs, these estimates reflect an upper limit. Females and juveniles are smaller and require less food than adult males.
So not only were the cheetahs responsible for fewer deaths, but they were also eating different species in the first place!
Some 60% of the cheetahs’ diet in the region consisted of wild animals, and 50% was made up of just kudu, duiker, steenbok, and hares. Despite the fact that domesticated livestock was more than three times as abundant in the area as game animals, the cheetahs mostly avoided it. This suggests that cheetahs prefer hunting native wildlife when possible. That alone should help ranchers rest easy.
While these data may help to exonerate cheetahs, it doesn’t explain why ranchers think that cheetahs are picking off so many of their springbok. Boast explains that it could be because springbok are declining in the area anyway. Since the early 1990s, the population has declined by more than 70%, as humans have encroached on their habitat and as the dry open plains springbok prefer are being replaced by a bush landscape, offering hungry predators more cover.
Further, unlike other predators, cheetahs are diurnal, so it’s likely that ranchers simply notice them more often. “This could lead farmers to presume that cheetahs are responsible for unexplained stock losses,” writes Boast.
Since cheetahs already prefer ordering native wildlife from the menu, the way forward for ranchers and conservationists might be to work together on maintaining healthy populations of native prey animals. – Jason G. Goldman | 23 March 2016
Source: Boast et al. (2016). Prey preferences of free-ranging cheetahs on farmland: scat analysis versus farmers’ perceptions. African Journal of Ecology. DOI: 10.1111/aje.12296.
Header image: ©Sean Garritt
source
No comments:
Post a Comment