Field Notes: February 2012
Read about the latest Earthwatch discoveries, rare sightings and exciting news reported by volunteers and scientists from the field.
Newly-described species of mouse lemur in Madagascar raises conservation concerns
Scientists in Madagascar have discovered what may be a new species of mouse lemur.
The researchers – who included Jonah H. Ratsimbazafy, lead scientist from former Earthwatch project Lemurs and forests of Madagascar - made the finding while visiting an understudied region in the east of the island, in a lowland rainforest site close to the Mantadia National Park.
They were collecting distributional data on mouse lemurs inhabiting the Sahafina forest, and found that the creatures didn’t match up precisely to any known mouse lemur species. They described the species in a paper published in international journal Primates, naming it Microcebus gerpi after the Malagasy organisation GERP (Groupe d’Etude et de Recherche sur les Primates de Madagascar), which is dedicated to research on and the conservation of lemurs.
The distribution of the newly described mouse lemur is not fully known, but seems to be restricted and highly fragmented, which raises serious conservation concerns. More data on many of its traits – such as behaviour, ecology and reproduction habits - are also needed to strengthen and confirm its species status.
Madagascar contains more than 20 percent of all described primate species on 0.39 percent of the world’s land area. Two of the 15 existing lemur genera contribute substantially to this extraordinarily high species richness, comprising sportive lemurs and mouse lemurs with 24 and 18 known species, respectively. If Microcebus gerpi is found to be a new species, it will raise the latter total to 19.
During the fielding period of Lemurs and Forests of Madagascar Earthwatch volunteers recorded that one species of lemur (Varecia v. variegate) fed on a plant species that had not yet been included in the list of food eaten by the animals. This discovery of a more diverse food source led to a better understanding of the feeding ecology of the species, helping to ensure an effective habitat for the lemurs.
“Head honcho” marmots with large gangs should watch their backs, says new study
An important detail to understand for scientists studying social animals that live in family groups is the relationship between the makeup of the group - who’s the dominant male and female, and who are the subordinates?
For the marmot, it’s important for the dominant male “boss” to stay in charge for the long-term, as well as ensure that he is the one having the babies with the dominant female.
In the case of the marmots that live in the French Alps, it turns out that the number of subordinates is a critical factor in determining the reproductive success of the dominant male. In fact, the head honchos with the larger gangs may need to watch their backs, according to a new study by Earthwatch scientists.
“Many people are interested in determining the benefits of being a social animal,” says Dr. Sophie Lardy, a zoologist and scientific team member on Earthwatch project Of Mountains and Marmots: Climate Change in the French Alps, led by Dr. Aurélie Cohas. “But this study is interested in finding out the costs.”
The team - who are continuing 20 years of research on these giant squirrels - said the dominant male marmots make a trade-off between the costs and benefits of having subordinate males in their family groups.
It’s good to have a lot of helpers around, but not so many that you risk losing your position as head honcho.
Alpine marmots live in family groups of up to 20 individuals. Each family has a dominant pair and several subordinate “helpers.” The main goals of the dominant male are to monopolise reproduction, and to hold on to their status for as long as possible. It seems the most successful male marmots in the Alps retain their dominance for up to 11 years, whereas others lose it after about five, Dr. Lardy said.
It’s tough at the top, and if a lot of subordinate males are around, the team found that it’s likely that the head honcho loses his rank in the following year. This pattern is consistent with what’s called the ‘‘limited control’’ hypothesis, which says that no matter how hard they try, some dominant males simply cannot control all the reproduction of the group.
What’s more, size may also matter in the marmot world, found Dr. Lardy. Body mass helps Alpine marmot males maintain dominance over their helpers - but because it’s hard work to be the one in control the whole time, the head honchos risk burning up their body mass over time. If the boss has a large number of helpers to manage, or fend off, then the risk is even greater.
After all, a skinny - albeit dominant male - may not be as effective at guarding his mate, so he could lose the dominance badge of honor. The researchers found that males that lose dominance are indeed lighter than those that maintain their dominance from one year to the next.
The next steps for Lardy and her team will be to see what the evolutionary consequences of this competition between marmots are, by monitoring the lives of individual marmots.
Earthwatch volunteers interested in studying marmots in the stunning French Alps will be able to collect data to help continue this important research. Complete findings from this study can be found in the paper Paternity and Dominance Loss in Male Breeders: The Cost of Helpers in a Cooperatively Breeding Mammal, published online at www.plosone.org.
There are only a few other studies on dominance in social animals – including research carried out by Earthwatch scientist Prof. Tim Clutton-Brock on Earthwatch project Meet the Meerkats of the Kalahari.
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