Research funded by the Royal Zoological Society of Scotland (RZSS), the charity that owns Edinburgh Zoo and the Highland Wildlife Park, is hoping to solve a pygmy hippo reproductive mystery as to why more females are born than males in captivity. With 60% of offspring born being female, researchers are working to find out whether this is problem restricted to zoo collections or is repeated in the wild.
The research coordinated by Institute of Breeding Rare and Endangered African Mammals (IBREAM) is looking into the female reproductive process of the endangered pygmy hippopotamus (Choeropsis liberiensis) as well as aiming to get more accurate population numbers and insights in the sex ratio of this species in its natural environment. In the 1990s wild population estimates for pygmy hippos stood at just 3,000 individuals but experts fear that these maybe exaggerated and that the true picture is a lot more serious. And the future looks even bleaker, with the world authority on conservation monitoring (IUCN) suggesting populations will continue to decline by at least 20% over the next 20 years.
Restricted to a 5,000 km² area of West Africa, scientists are focusing on the hippo hotspot of the Tai National Park, West Africa and are using camera tracking techniques to monitor behavior and numbers present. As they are mainly active at night this is the most effective way to see what they get up to. As Dr Monique Paris, IBREAM Research Director based in the Netherlands explains, the research is key to helping create viable captive populations should this species go extinct in the wild.
“There are clear reasons as to why populations have declined in the wild, such as habitat loss and hunting, but for those working with captive populations there are equally puzzling questions. With the endangered status of the hippo, maintaining a viable population in captivity is important. However for every two males born, three female babies are born making zoo management complex. We are also dealing with extremely shy animals with little knowledge of their natural behaviour and therefore we really don’t know if this is purely a natural reproductive phenomenon or one restricted to the captive environment.”
Edinburgh Zoo is home to three pygmy hippos, with one female born last year. Iain Valentine, RZSS’ Director of Animals, Education and Conservation, said:
“For scientists to ensure genetic diversity in captive stocks, it is important to work out why genetically valuable females may not be breeding. But to do this, we need better understanding of the natural cycles to make sure that we can do all we can in the captive environment. That is why RZSS is part of this pioneering conservation partnership and is funding primary research that will help the whole zoo community. This will hopefully give this species of hippo a fighting chance in the wild.”
The first images using motion-sensitive cameras have now been received and are already helping scientist to monitor numbers as well as behaviour. In addition to the hippos, so far three other species of deer [Jentink duiker (Cephalophus jentinki), Maxwell duiker (Cephalophus maxwelli) and Zebra duiker (Cephalophus zebra)] along with elephants and leopards, have been photographed.
The project is co-founded by the Prince Bernard Foundation and on-the-ground field work is a collaboration with colleagues Dr Karim Ouattara and Dr Inza Kone at Cocody University (Abidjan), and Centre Suisse de Recherches Scientifiques (Abidjan), and students from the Netherlands (Mark van Heukelum and Henk Eshuis) are currently assisting with the camera trapping studies. In addition, IBREAM is also studying fecal samples from 15 zoological institutions throughout Europe to help evaluate female hippos’ monthly cycles and if hormones found in the poo can show whether a female is pregnant or not.
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