Lemurs go out at night
by Kurt Kleiner
Keeping up with ring-tailed lemurs is hard enough during the day, as the cat-sized primates leap and run through tree branches. Figuring out what they do at night is even harder, and until recently the scientific consensus was that ring-tailed lemurs probably just curled up and went to sleep.
Now Joyce Parga, UTSC professor of anthropology, has shown in a paper in the journal Primates that troops of ring-tailed lemurs actually travel around at night and even interact with other troops. The work could lead to better understanding ring-tailed lemur sociality and sexuality.
Parga has been studying ring-tailed lemurs for more than a decade. The animals are native to Madagascar, but Parga has been working with a group of about 60 free-ranging animals on a reserve on St. Catherines Island, Georgia.
In previous work she would sometimes discover that an animal which had been in one location as dark fell would turn up at another location before first light. But night travelling had never been firmly documented.
So Parga fitted five lemurs with small GPS collars which recorded their movements. After a week, she collected the collars and downloaded the data. She had expected to see fairly short movements of individuals, mostly around twilight. Most likely, she thought, would be low-ranked males travelling in search of females in other troops with which to mate.
Instead, her data suggest that entire troops moved together, often travelling relatively large distances – 2,100 meters, in one case. And on one night, two different travelling troops encountered each other and interacted.
“I never dreamed I would see true night-ranging,” she says.
The reason for the night travelling isn’t clear. It could still be prompted by males looking for mates, while the whole troop follows along. But that would be unusual, since in lemurs females are dominant and generally initiate group movements.
When Parga began tracking, a number of females were in estrus and sexually receptive. As the week went on and females completed their estrus cycles the night-range was reduced, which could suggest that mating really was behind the movement. But the moon was also waning during the week, providing less light for the lemurs to see.
Parga says that in the spring, she hopes to track the lemurs for a longer time period.
"Dr. Parga’s findings are fascinating and underscore how much more we have to discover about the other animals with which we share the planet,” says Malcolm Campbell, UTSC vice-principal, research.
“Dr. Parga’s wonderful work is beautifully aligned with other research efforts at UTSC, which aim to characterise the remarkable activities of our fellow animals on Earth. Such findings not only better inform us of the incredible diversity of life on Earth, but help better guide efforts aimed at protecting and conserving biodiversity. The characterisation, protection and conservation of biodiversity is a key research theme at UTSC, with relevance on a local and global scales. Dr. Parga’s work is a perfect exemplar of research that fits within that theme."
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