Life Photo Meme: Royal

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Felidae

The lion (Panthera leo) has long been know as the king of the jungle. It is the second largest cat, with males weighing in at 250 kg (550 lbs) and about 2 m (6 ft) in length. However, this is nothing compared to the ancient American lion, the largest lions ever to have existed at 300 kg (660 lbs) and 2.5 m (8 ft).

Most people know about the superb hunting skills that the lionesses practice, and that the males basically do nothing but defend their pride from other male lions. Lions are the only cat to have sexual dimorphism, as the males have a distinctive mane. Some relatively recent research had some interesting things to say about the mane, in terms of selection and possible purpose. They found that males with darker longer manes were more likely to win male competitions, and be successful at mating. So, males may be able to size up their competition by comparing manes. But, males with darker manes had more difficulties in hotter weather conditions, to the extreme that their sperm can be come deformed. Of course, there is the idea that having a handicap to over come means that you are very healthy, and would make a good mate (think peacock tails). The original study can be found here.

Photohunter: Beautiful

I thought I'd put up a classic beauty. This guy, like many other males in the animal kingdom, has resorted to flashy, bright, and beautiful colors to attract the females. So the question is, why? Females put a lot of effort into reproduction; eggs are more energetically costly to make than sperm, not to mention the costs of rearing the chick after it is laid. Females typically (at least on land) mate fewer times than males, and with fewer individuals. Because of that, females are super choosy about who they do mate with, often wanting to make sure that they are getting the 'best genes' for their offspring.

Their choosiness often results in visual signals of a male's health and well being. In this case, by growing a long tail, they show they can gather enough food to grow such a tail and are still strong or fast enough to escape predators. The size of the eyespots on the tail has been linked with size of the bird as a hatchling. So picking guys with bigger eyespots may give the female bigger chicks. Bright plumage means that the bird does not have any parasites, this may mean that the male has some nice anti-parasite genes to pass on, or at the very least, that the female won't get any parasites while mating with him.

In short, this beautiful eye-candy is meant to show the females that they are quality picks.

Playing dead

Just read a neat paper on the heritability of death feigning and how it may be selected for in the wild by Miyatake et al. (2004). Death feigning is when a creature pretends to be dead, either by falling off a twig and curling up its legs, or by freezing, presumably to escape predation. The gray death-feigning beetle pictured above can feign death for up to thirty minutes (according to the beetle dealer). What Miyatake and the others wanted to know was, is this death-feigning ability heritable, and does it actually help them escape predation?

So they took 200 red flour beetles and recorded how long they played dead for after touching them with a stick. The 10 males and 10 females who feigned death the longest were used to start a long line, and the 10 males and 10 females who feigned death the shortest were used to start a short line. They then repeated this procedure for ten generations, allowing only the 20 longest feigners and 20 shortest feigners to reproduce each generation.

After ten generations, they found that the long line feigned death for a longer period of time than the short line did. The long line feigned death for over a minute and a half, while the short line only feigned death for about 5 seconds. They also found a difference in the numbers of individuals who actually feigned death. What they saw was 86% of the long-line individuals feigned death, while only 7% of the short-line individuals feigned death.

So now they know that death feigning is heritable and can be selected for or against in nature, but does it actually work to help save them from predators? Will it actually be selected in nature? To find this out, they introduced a predator and recorded survivorship and behaviors of short-line and long-line individuals. What they found was that the jumper spider used as a predator would lose interest in the beetle if it feigned death. So most of the long-line individuals survived (64%), and most of the short-line beetles were eaten (73%).

So if the beetles have predators in an area that act like the jumper spider, you could expect that the beetles in those areas would have long death-feigning times, but in other areas without such predators, you may expect shorter feigning times. Now all you have to do is go out and test that!

Takahisa Miyatake, Kohji Katayamat, Yukari Takeda, Akiko Nakashima, Atsushi Sugita and Makoto Mizumoto. 2004. Is death-feigning adaptive? Heritable variation in fitness difference of death-feigning behaviour. Proceedings of the Royal Society B. 271: 2293-2296