Monday, November 01, 2010

Senegal: On the trail of a dead manatee

Last June an adult female manatee died in a narrow lagoon called Mbodiene. I try to follow up on all of these reports since any information we can gather adds to our sparse knowledge of the species. This manatee was particularly interesting because it had been seen alive with 2-3 others several days before it died, and photos and reports clearly indicated it was in distress. Unfortunately I was in the USA at the time and could not get to the site myself. Due to the somewhat slow chain of communication, after the manatee died no one could get to the site fast enough to collect samples before the local population butchered the carcass for meat. There were enough witnesses to verify that the manatee did die naturally, it was not killed. Several people tried to help it as it struggled to breathe. But unfortunately once it died, people couldn't imagine seeing the meat "go to waste".

In this photo the manatee propels itself high out of the water as a concerned man tries to help it. Based on this photo and others showing it bobbing on the water's surface, it is possible the manatee had a watercraft impact injury (I used to see lots of these in Florida and they are less obvious than manatees cut by boat propellers. Often the manatee has trouble diving because a broken rib bone has punctured a lung). Photo courtesy of Oceanium Dakar.
My guess is there was little anyone could've done to save it. There are no facilities in Africa to take care of injured or sick manatees (or any other marine mammals for that matter!).

People on scene claimed the other manatees with the distressed one were it's "babies" because they were smaller, but based on descriptions I got, I think these were just other individuals accompanying it. Female manatees are larger than males, and it's a common mistake for people to think males are babies, or that manatees travel in "family groups" (also not true, they form temporary social groups for feeding, socializing or mating, but these are not related individuals). Ultimately the other manatees headed out of the lagoon back to the Atlantic Ocean. Here in Senegal manatees are commonly reported near shore in the ocean moving between different lagoons/estuaries.

So last week I went to Joal to meet with Karim Sall, a biologist who is involved with mangroves, sea turtles, and marine mammals in the Delta Saloum region. Aside from wanting to meet him because he has lived in the area for many years and is a great source of local information, I was specifically hoping to learn more about a manatee that died in Mbodiene Lagoon. Karim told me at first he thought the manatees had become accidentally trapped in the narrow lagoon, but after talking to some old men there he discovered there are at least 2 freshwater springs within it and that manatees are sighted annually, mostly between March and May. This is interesting because that's the end of the dry season, so manatees may be migrating along the coast and using the springs as a stopover for freshwater. The lagoon is only 9km long and about 200 feet wide, so manatees are easy to spot when they're there.

Karim (right) searches his computer for pictures he took of the manatee remains.
This is the photo he gave me. By the time Karim got to the site last June, the manatee had been completely butchered and only pieces of skin were left. I will use a piece of the dried tissue for genetics. Photo courtesy of K. Sall. After talking to Karim, I went out to the lagoon. I went to the site where the manatee died to collect a GPS point and see the area for myself. There were mangroves along the edge but no visible seagrasses or other aquatic plants. Although I checked at several houses, no one who had seen the manatee was around, but the site visit helps me learn about manatee use areas for the future. I'd like to find the springs and document those as well... there's a huge network of freshwater springs that manatees use in this region.

Mbodiene Lagoon is very narrow and shallow, especially at low tide.

On the way home we saw this sign for Pointe Sarene with a manatee caricature on it. Pt. Sarene also has a freshwater spring It may seem like these little bits and pieces of information, gathered so long after the manatee died, are not much. But when we know so little, every bit helps to piece together the African manatee's life history.

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