送交者: xj 于 2005-4-06, 14:41:20:
回答: 继续胡说八道 由 boxer 于 2005-4-06, 13:40:41:
other methods such as painting are hard to track because birds may eat the whole cricket bodies. One advantage of using radio is to track the movement of cricket herds. The disadvantage is radio will affect cricket's movement, as you've already mentioned.
A large cluster of crickets will attract lots of birds. It is possible that all crickets will be eaten as time goes by. I think there is a threshold at which the cricket population is big enough to sustain themselves.
On the other hand, a cricket can hind somewhere which is hard to be found by bird, thus increasing his survival.
The way of you defining sample space is confusing. The bird space is illy defined, and the probability of being eaten is the aim of this study, not the assumption.
The study is sort of follow up study using capture recapture method (not exactly). You randomly select a sample of crickets and send back to the cricket population. Naturally, some crickets will leave behind the group, while others stay in the group, thus basically dividing the whole cricket population into isolated crickets and clustered crickets.
I am not sure how the authors did the analysis but one simple way is to compare those isolated radio carriers with those clustered radio carriers, without extropolating to the whole cricket population. This will avoid the assumption that radio carrier will be evenly distributed between isolated and clustered crickets.
There are many examples of this kind ecological research. Nothing is earthshaking but somebody has to do it. It is for practicle reasons.