Wildlife of the Mangroves

New research reveals the richness of Madagascar’s mangrove birds and lemurs

By Blue Ventures

August 26^th, 2016

“Quick, up there - eyeshine!”

Spinning around with torch in hand, I illuminated the tops of the nearest trees and eventually saw them – two bright, sparkling eyes high in the branches, reflected in my torchlight. It must be a fruit bat, I thought. After all we were standing on a tiny island deep within one of Madagascar’s mangrove forests, and the mainland was over two miles away. What other animal could possibly be living out here?

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Swamp lemurs

But it wasn’t a bat at all, it was a lemur. A northern giant mouse lemur no less, an endangered species that only lives in this corner of northwest Madagascar. It wasn’t even the first lemur our Blue Forests team had found in these mangroves, as our Geospatial Scientist Zo Andriamahenina had come across two Critically Endangered Claire’s mouse lemurs just up the creek, only a month before.

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Mangroves are incredibly important ecosystems that provide us with a range of ‘ecosystem services’ – they protect coastlines from storms and tsunamis, provide nurseries and feeding grounds for many of the fish and crustaceans we eat, and they can even store more carbon than tropical rainforests!

Amazingly though, we still know very little about their importance for terrestrial wildlife. Even in Madagascar, which many people consider the world’s top conservation priority and which is amongst the top 15 mangrove-rich countries, we knew almost nothing about the birds and animals that use these rich forests.

Seeing the northern giant mouse lemur inspired us to change that.

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Crowdsourcing science

If we had seen two lemur species in the mangrove, perhaps others had too? I had already ploughed through all the scientific literature and only found records of four lemur species using mangroves, but I hypothesised that others may have made similar observations that they had never published.

So I decided to crowdsource, and put together a database of over 1200 people, including scientists, conservationists and tour operators, that may have ventured into Madagascar’s mangroves. I emailed them all, and the observations they shared astonished me.

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It turns out that at least 23 lemur species have been seen using mangroves – more than 20% of all lemurs and more than half the species that have mangroves in their ranges. While many were small, nocturnal species, the list included such charismatic creatures as the ring-tailed lemur, several species of leaping sifaka, and the mysterious aye-aye.

Not all the observations could be identified to species level, but of those that could 20 species are listed on the World Conservation Union’s Red List of Threatened Species – four are Critically Endangered, 13 are Endangered and three are Vulnerable. Mangroves could be much more important for their conservation than we realised.

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Lemurs aren’t the only terrestrial animals using the mangroves, and in fact weren’t even the initial focus of our research - we were there to research birds. Birdwatching is a popular activity amongst nature lovers, so we wanted to know which bird species could be seen in the mangroves of Ambanja and Ambaro Bays as part of our project to develop community-based ecotourism in the area.

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We surveyed the birds of three sites in the bay, and the results were almost as astonishing as those of the lemur study. We recorded 73 species, including such rarities as the Madagascar fish eagle, Madagascar pond-heron and Madagascar teal. These birds were all known to use mangroves but, given their threatened status, we were delighted to find them all the same.

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What really surprised us was the number of recorded species that are more typically found in the country’s rainforests and dry forests, and many of which had never been recorded in mangroves before. A quarter of the species we saw exist only in Madagascar, including such colourful gems as the crested coua and chabert vanga, while over half exist only in the western Indian Ocean.

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local knowledge

As we were only surveying the mangroves for a few days, we knew that we might miss some of the more uncommon or seasonal species, and thus reveal only a partial picture of the mangrove’s true diversity. The Blue Forests team are fortunate enough to work closely with fisher communities in this area, and so we set out to involve them directly in the research process, hoping to use their experience to add to our list.

Fishers use the mangroves day in, day out, and have an incredible knowledge of the birds that live in them. However, this method of data collection has a flaw that can quickly become apparent – if we don’t use the same names as the fishers, how can we be sure that we’re talking about the same species?

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We overcame this problem with the help of the community groups that manage the mangroves of Ambanja and Ambaro Bays. We went with them into the mangroves and were taught the local names for every bird that we saw, before sitting with them to carry out in-depth interviews.

Armed with field guides full of pictures and – most importantly – an MP3 player full of bird calls, we were able to ascertain that fishers knew of at least 18 additional species from the mangroves in addition to those we had seen ourselves. In reality there may be many more, since the fishers didn’t distinguish between many species of similar looking shorebirds and seabird.

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A real haven for wildlife

In total at least 99 species of bird are now known to use Madagascar’s mangroves, almost 40% of all bird species ever recorded in the country. When we consider that a fifth of all lemurs also use them, it’s clear that mangroves may actually be much more important for the conservation of the country’s unique wildlife than we had ever realised.

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Mangrove conservation efforts in Madagascar are still at an early stage, and tend to focus on securing the irreplaceable services that these marine forests provide, such as storing carbon and maintaining fisheries. Raising global awareness of the magnificent wildlife inhabiting mangroves can only help inspire and increase this conservation effort.