Sign up for our email newsletter for the latest science news Now we had all the pieces we needed. Multiplying the population density by the area in which T. rex lived ...

Billions of Tyrannosaurus rex roamed North America during their fascinating reign as top predators, according to a team of researchers that went about the daunting task of making the calculation.

In this paper, we describe a method for estimating animal population density per unit area from mark, release, recapture (MRR) data. Standard procedures are available for estimating population size ...

Biologists have long counted songs to get an idea of bird abundance but it is much harder to work out the actual density. The sound recordings from a microphone placed in forests or woods can now be ...