330 Gregory H. Adler
807060504030(^2014)
4
5
51
52
9
8
Controls 12
Experimentals
10
0
10 15 20 25
Number of fruiting trees per hectare
Number of spiny rats per hectare Figure 19.3 Effects of provisioned food on
mean population density of spiny rats
compared with control populations in relation
to natural fruit availability (from Adler 1998).
Numbers represent island designations.
12
Controls
Experimentals
8 7 6 5 4 3 2 1 0
8
9
52
51
5
14
4
10 15 20
Number of fruiting trees per hectare
Number of spiny rats per hectare
25
Figure 19.4 Effects of provisioned food on
mean density of known births of spiny rats
compared with control populations in relation to
natural fruit availability (from Adler 1998).
Numbers represent island designations.
To test the second hypothesis regarding
responses during periods of resource scarcity, I
used similar methods but increased the number
of experimental populations to eight and pro-
visioned the populations from November 1997
through January 1998 and from November 1998
throughJanuary1999whenfruitproductiontyp-
ically was lowest. I provisioned each population
with cracked corn (which is eaten by spiny rats)
because sufficient fresh native fruit was unavail-
able. I provisioned each experimental population
every week (except during the week in which rats
were censused) at the rate of 50 kg ha−^1 , again
using permanently placed exclosures at a density
of 10 per hectare.
Of the eight experimental populations, six
reached higher densities than would have been
expected based on the quantity of natural fruit
available when compared with the controls. The
two experimental populations that did not reach
higher densities were at extremely low densi-
ties at the beginning of the study but increased
steadily throughout the 2-year study period, but it
is not possible to determine if the increase was