The eighth continent. The “naturalist’s promised land”. A true lost world, this was a place where only a millennium ago there were eight-foot tall birds and lemurs as large as gorillas. Madagascar is the world’s largest oceanic island, bigger than California and slightly smaller than Texas. It is the hottest biodiversity hotspot in the world, leading in terms of endemic species and the fact that only 10% of its original forest is left standing.
Despite the fact that Madagascar is almost denuded, there are still areas that have yet to be explored. It truly is one of the last frontiers. The tally of 200,000 species living in Madagascar (75% of which can be found nowhere else in the world) might be underestimating the true biological wealth of this island. However, there is trouble in this naturalist’s paradise. This distinctive biodiversity is under threat due to a quickly growing, impoverished population, political instability and a lack of a centralized, concerted effort focused on sustainably managing natural resources and conserving threatened wildlife populations. Almost half of Madagascar’s known vertebrate species are listed as Vulnerable, Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN), meaning that they face a high risk of extinction in the wild.
Three factors drive biodiversity loss in Madagascar: habitat loss, poaching and exotic species.
When Species Lose their Homes (Habitat Loss)
In addition to becoming smaller, reduced patches of habitat can become vulnerable to outside influences (edge effects). The more space between habitat patches there is, the harder it can be for animals to move safely between each patch, which can make it difficult for animals to find food, shelter and mates. This increases the chance that a population will go extinct. Between the 1950s and the early 2000s, Madagascar lost almost half of its forest cover.
Many of Madagascar’s species are unable to live without the forest. Studies have shown that all types of animals, from birds to amphibians to tenrecs (endemic small mammals) are negatively affected by habitat loss and fragmentation, with more and more species disappearing from habitat patches as they get smaller and smaller. Having large swaths of connected, undisturbed habitat seems to be especially important to Malagasy carnivores.
The former President of Madagascar, Marc Ravalomanana, attempted to save the forests. Unfortunately, with the 2009 political crisis, logging—illegal and legal—has increased, continuing the slow, creeping destruction of habitat. Zach Farris’ (and now, my) study is the first to examine the effects of habitat loss on species on a large spatial and temporal scale in northeastern Madagascar.
Snares and Guns (Poaching)
Where there are people in Madagascar, you can assume that they are hunting native species. Although it is widespread, poaching (or bushmeat hunting) and how it affects species in Madagascar is little studied. In countries where the government doesn’t back conservation, poaching feeds families and provides income, all significant benefits when compared to the relatively small risks of maybe being captured and fined for the illegal activity. It is likely, due to the current political instability, that poaching in Madagascar is now significantly more rewarding and less risky.
In and around Makira, where the annual income is around $70 (US), almost a quarter of that income can come from hunting. The average household spends almost half the year annually setting up snares or tracking carnivores to hunt. However, these people are not eating native species because they prefer them. They would prefer to eat domestic sources of meat like chicken or zebu (cow), but replacing bushmeat with zebu or chicken is very expensive, making it unreasonable on a Malagasy budget.
Where fady (social taboos) will not allow people to eat or hunt certain species, carnivores are still killed if they threaten—or are believed to threaten—chickens. This is because chickens are much more valuable to locals than native carnivores.
Personal anecdote: I have heard that a fossa (dead) costs around 3,000 Ar ($1.50) while a chicken costs 8,000 Ar ($4).
Stranger Danger (Exotic Species)
Another driver in the loss of species around the world, the problem of exotic species is exacerbated by the already mentioned threat of habitat loss. Habitat disturbance creates habitats that are favorable to exotic species. The more numerous exotic species can then gang up on the native species, who are already suffering from having their home changed in a way that doesn’t suit them.
Madagascar has many exotic plant and animal species, but my study is most concerned with the impacts of four exotic mammals present in Makira: the domestic/wild cat (Felis spp.), the domestic dog (Canis familiaris), the small Indian civet (Viverricula indica) and the black rat (Rattus rattus).
Fluffy is a killer: Anyone who has watched a cat fat from bowls of food stalk down a bird in their backyard can attest to the fact that cats are extremely opportunistic hunters. However, not everyone knows that cats have contributed to at least ten percent of modern extinctions. Studies in Madagascar have shown that cats hunt lemurs and that more cats in the forest present problems for some of the smaller native carnivores. Both domestic and wild cats were introduced to Madagascar; no one knows whether the forest cats are one, the other or some sort of super-hybrid. We do know, however, that they spell trouble for any native species smaller than them.
Fido spreads diseases: Dogs now live all over the world. Although free-ranging dogs can hunt and kill other animals, the greatest impact dogs might have on wild populations—especially native carnivores—is that of spreading diseases like canine distemper. In other countries, several studies have shown that when dogs and wild carnivores get in contact with each other, it’s usually the wild carnivores that lose in the end. Dogs might also be effective interference competitors, especially with medium- and small-sized carnivores and studies have shown dogs preying upon lemurs.
The deadly mimic: The small Indian civet is widespread in southeast Asia, where it is native. It seems to benefit from habitat disturbance. No one has observed it yet, but it is believed that civets might be able to hunt and kill lemurs. Other studies have suggested that civets might cause trouble with the smaller carnivores.
Rats, rats, rats! Wily and hard to pin down, think of rats as the perp that everyone knows did it, but no can quite prove it. There is currently no concrete evidence that introduced rats have displaced native small mammals on islands through competition, although they have black rat been implicated in more than ten percent of the extinctions since the 1500s. Rats can be vicious predators (especially of ground-nesting birds) but in regards to Madagascar, black rats might be using biological weapons in their war: the plague, which is deadly to the native small mammals.
These three threats continue to ravage Madagascar, with no end in sight. Species that have yet to be discovered are potentially going extinct. Trees are being felled. The magic of Madagascar is being lost, slowly but surely. So what is there to do? Check out the next page, Carnivores and Conservation, for the next installment!
And if you wish to read what you have just read but in fancy-schmancy science-y language, click here!