Tuesday, 27 April 2010

Abstracts: Koala Birth Seasonality

Just because you can breed continuously throughout the year doesn't mean you can, or you should. Animals that breed throughout the year can have higher fitness, but only if there's enough resources available that the young aren't a major drag for future reproduction. Also, having accurate breeding information is important for establishing even basic demographic information, as it can push which demographic model you use.
Establishing accurate demographic information for free-ranging populations of animals is difficult without knowledge of individual chronological age. We estimated the birth dates of 743 koala (Phascolarctos cinereus) joeys at 3 sites in Queensland, Australia, using body mass obtained from a reference population with known birth dates. From these age estimates we compared the annual distribution of births across calendar months. At all 3 locations about 60% of births occurred between December and March. The annual pattern of births was identical for males and females within locations, but overall annual patterns of births differed between the southern and northern sites. We conclude that koalas can bear offspring in every month of the year, but breed seasonally across Australia, and that a sex bias in the timing of births is absent from most regions.
The reason they include the bit about the sex bias is because previous authors (McLean and Handasyde 2006) found one in an island population of Victoria Koalas.

doi: 10.1644/08-MAMM-A-358R.1.

2 comments:

Cate said...

Hey, I was thinking that you are the perfect person to ask this question. With the advent of Earth Day and watching Food, Inc., I began to consider the carbon impact of village life -- well, I mean, I've thought of it before and tried to think of ways to make it less, but now I framed it differently in my mind. So we don't have cars or semis out here, but we do have 6-10 small planes per day bringing in everything we use/eat, and then the jet/cargo planes before that. And then we have all these little engines -- I mean, they're little, but they are probably not as efficient as car engines. So for a village of 1100-1200 people, I'm wondering if we have the carbon footprint of a much larger urban town -- would you have a guess as to what size town in urban America? Or am I figuring this wrong? You are the numbers guy, that's why I'm asking you this. :)

TwoYaks said...

That's an excellent question, and one I'll have to think about. It's very tricky...