Data from: Territory size decreases minimally with increasing food abundance in stream salmonids: implications for population regulation

How the local density of territorial animals responds to changes in food
abundance will depend on the flexibility of territory size. Quantitative
estimates of territory size over a broad range of food abundance are
relatively rare because of the difficulty of measuring food abundance in
the wild. Stream salmonids are an ideal model system for investigating
flexibility in territory size, because food abundance can be quantified in
the field and manipulated in the laboratory. We conducted a meta-analysis
to test whether territory size decreases with increasing food abundance,
and a mixed model analysis to test among three competing predictions: with
increasing food abundance, territory size will be (1) fixed – the slope of
a regression of log territory size vs. log food abundance = 0; (2)
flexible and decreasing, as if individuals are defending a fixed amount of
food – a slope = -1; and (3) initially compressible, but with an
asymptotic minimum size – a slope between 0 and -1. We collected data from
16 studies that manipulated or measured food abundance while monitoring
changes in territory size of young-of-the-year salmonids; 10 were
experimental laboratory studies, whereas six were observational field
studies. Overall, territory size decreased significantly with increasing
food abundance; the weighted average correlation coefficient was -0.31.
However, the estimated slope of the relationship between log territory
size and log food abundance was only -0.23, significantly different from
0, but also significantly shallower than -1. Our estimated slope suggests
that attempts to increase the density of territorial salmonids by
increasing food abundance and reducing territory size will be inefficient;
a 20-fold increase in food abundance would be required to double
population density. Our analysis may also have implications for other
species with a territorial mosaic social system – i.e. contiguous
territories. In these social systems, social inertia will dampen any
effects of changes in food abundance on the local density of settlers,
compared to non-territorial species or those with non-contiguous
territories.