- At least 23 species of lemur in five families have been spotted in mangroves, about 20 percent of all lemur species and about half of the species whose range is known to include mangrove areas.
- In Madagascar, mangrove extent declined by 21 percent between 1990 and 2010, according to a study released in January 2016.
- It’s difficult to say how important mangroves are for lemurs without further research, however.
In March 2015, Charlie Gardner and his wife were performing a bird survey for the marine conservation organisation Blue Ventures deep in the mangroves of northwest Madagascar.
They went for a walk one night and had just turned back toward their camp as it started to rain when they noticed the glimmer of a mammal’s eyes high in a tree. Being that there was about three kilometers (nearly two miles) of mangrove swamp between them and the nearest dry land, Gardner and his wife assumed it must be a fruit bat. But as they got closer, they realized it was in fact a Northern Giant Mouse Lemur (Mirza zaza), an endangered species found only in that particular part of Madagascar.
Gardner, an honorary research fellow in biodiversity management at the University of Kent, had seen ring-tailed lemurs in mangroves near where he lived in southern Madagascar many years prior to this sighting, and had been interested in this behavior ever since. But after searching all the literature he could find, he realized that only four species of lemur had ever been recorded in mangrove habitat.
But then, last year, Zo Andriamahenina, a geospatial scientist for Blue Ventures, found two Claire’s mouse lemurs in a mangrove up north, in Antsahampano — the same mangrove forest where Gardner and his wife encountered the Northern Giant Mouse Lemur.
These discoveries were surprising, to say the least, Gardner told Mongabay: “On the one hand it was surprising because mangroves are a difficult environment to live in. They are regularly flooded by seawater, they tend not to harbor great invertebrate diversity above the water, and they are floristically very poor — in fact in all of Madagascar there are just eight mangrove species, and many stands are composed of just two or three species. So all in all we would not expect there to be much for lemurs to eat year-round.”
Gardner continued: “On the other hand the lack of records might just be because no one has ever really looked.”
Mangroves are difficult places to conduct research, he explained. “The trees grow incredibly densely and many have horizontal stilt roots that make passing impossible, and of course you always have to travel either through water or deep, cloying mud.” Plus, given that Madagascar’s terrestrial forests are so rich in lemurs, “Why would a primatologist ever look in the mangrove?”
Gardner himself doesn’t typically spend much time in mangroves, but had still come across lemurs in mangroves twice now, leading him to hypothesize that many others might have had similar encounters. So he set out to collect as much anecdotal evidence as he could to supplement his review of the existing literature on the topic. He surveyed hundreds of scientists and conservationists as well as a variety of other people who might have spotted a lemur in a mangrove at some point in the past.
“I knew that I had to contact more than just scientists — after all, I already knew that primatologists rarely went near mangroves — so I also focused on ecotourism guides, hotel staff in coastal areas and so on,” he said. “In all I wrote to over 1200 people.”
The results of Gardner’s study were published in the International Journal of Primatology in April. He found that at least 23 species of lemur in five families have been spotted in mangroves, about 20 percent of all lemur species and about half of the species whose range is known to include mangrove areas.
“Lemurs used mangroves for foraging, sleeping, and traveling between terrestrial forest patches, and some were observed as much as 3 km from the nearest permanently dry land,” Gardner wrote in the study. “However, most records were anecdotal and thus tell us little about lemur ecology in this habitat.”
Still, this is pretty conclusive evidence that mangroves are more widely used by lemurs than has previously been thought. And since 94 percent of lemur species are threatened with extinction, mangroves “merit greater attention from primate researchers and conservationists in Madagascar,” Gardner wrote.
“Given that mangroves are among the most threatened of all tropical ecosystems (Duke et al. 2007; Valiela et al. 2001) and have lost 20%–35% of their global extent since 1980 (FAO 2007; Polidoro et al. 2010; Valiela et al. 2001), an understanding of their role in maintaining primate populations is essential to inform conservation planning, as well as contributing to our knowledge and understanding of primate–habitat interactions,” per the study.
In Madagascar, mangrove extent declined by 21 percent between 1990 and 2010, according to a study released in January 2016.
It’s difficult to say how important mangroves are for lemurs without further research, however. For several of the widespread species Gardner found reports of in mangroves, like the ring tailed lemur, aye-aye, and Coquerel’s sifaka, mangroves make up a tiny portion of their range, meaning mangroves are probably not hugely important for the conservation of those species.
But in northwest Madagascar, where the largest mangrove forests are, there are a number of threatened species — such as the critically endangered Claire’s mouse lemur, the endangered Danfoss’ mouse lemur, and the endangered Northern Giant Mouse Lemur — that only occur in small areas. “If these species are also at home in the mangroves, then that could be very significant,” Gardner said.
- Gardner, C. J. (2016). Use of Mangroves by Lemurs. International Journal of Primatology, 1-16. doi:10.1007/s10764-016-9905-1
- Jones, T. G., Glass, L., Gandhi, S., Ravaoarinorotsihoarana, L., Carro, A., Benson, L., … & Cripps, G. (2016). Madagascar’s mangroves: quantifying nation-wide and ecosystem specific dynamics, and detailed contemporary mapping of distinct ecosystems. Remote Sensing, 8(2), 106. doi:10.3390/rs8020106