It’s good to be omniscient.
Only a few natural studies have been able to approach that level of all-knowing knowledge. Peter and Rosemary Grant come fairly close in some seasons studying finches on the smaller Galapagos Islands. A new paper must must surely be a contender for god-like knowledge of a population of animals.
Rodríguez-Muñoz and colleagues basically became all-seeing and all-knowing to figure out what evolutionary pressures were being brought to bear on a population of crickets (Gryllus campestris). In other words, who’s getting it on with whom? Who’s being eaten? Those sorts of things.
To do this, they pulled off a rather astonishing video recording set-up of over 60 infra-red cameras that allowed them to monitor between 150-200 crickets all the time.
Let me say that again.
Every. Single. Cricket.
All. The. Time.
And lest you think this is in a controlled lab setting? No! This is a field in Spain! And lest you think this is just a series of snapshots of the population? No! They tagged each individual so they were able to identify them by name! And lest you think was some a few days? No! This was over two summers! And, just to top put a cherry on top, they did DNA work to identify parents and offspring.
And some say they did it while keeping six plates on rods spinning simultaneously and telling jokes.
Once you’ve got thousands of hours of video of crickets... what do you want to know? Because you probably have a good shot at answering the question, almost regardless of what it is.
A classic prediction in evolution and ethology is that most females have some reproductive success, but males tend to vary wildly in their success, with some being “super winners” and some being “super losers” (It’s rather like research.)
They did indeed find this pattern, but a surprise was that the female success was not as uniform as expected: many females had no offspring. They also found that the females had more offspring when they mated with multiple males. This is an effect that has been suggested in other research, but the comprehensive nature of this study makes this one of the best examples for the phenomenon to date. Indeed, females tended to have as many mates as males.
Another surprise was that dominant males had fewer offspring than subordinate males. The authors don’t have a ready explanation for why this is, more or less shrugging and saying, “Dominance doesn’t always predict mating success.”
Are there similar surprises waiting in survivorship? The story doesn’t seem to be as well fleshed out as the mating story. For instance, there’s not a major breakdown of the causes of death; mostly it’s just lifespan information.
The main behaviour that appeared to be linked to lifespan was singing in the males. Longer-lived males had sung more over their lives. This suggests that the ability to sing a lot is a good indicator of general health. And, for short-lived males, this was also correlated with more offspring. Oddly, though, there was no correlation between the amount of singing and amount of offspring for long-lived males.
With so many surprises, I’m sure there will be other papers to emerge from this massive recording session. And it will be interesting to see if other researchers can apply this high level of surveillance to other species that are larger or more mobile.
Rodriguez-Munoz, R., Bretman, A., Slate, J., Walling, C., & Tregenza, T. (2010). Natural and sexual selection in a wild insect population Science 328(5983): 1269-1272. DOI: 10.1126/science.1188102
Third picture by Gilles San Martin on Flickr, used under a Creative Commons license.