fig. 32.4), and this is often where control efforts are most in-
tensive (Brunton, Macdonald, and Buckle 1993; 1996; Quy
et al. 1992). The merit of neophobia as a general feature
of diet selection is therefore generally assumed rather than
proven, but the rat’s paranoid tendencies are of undeniable
value in a poison-rich environment. Yet, considering these
marked differences in attraction versus avoidance of novel
(often human-produced) foods, both species are extremely
successful in their association with humans. Not much is
known about dispersal patterns or distances in wild popu-
lations, but they must be pronounced, considering the wide-
spread distribution of both species.
It is also not clear why diseases are more readily associ-
ated with rats. Perhaps their more predatory nature com-
pared to mice and their greater predilection for water may
make them more likely to harbor zoonoses and waterborne
diseases, respectively. It is more likely, however, that the
rat’s reputation may be a consequence of its greater visibil-
ity, its involvement in some very prominent diseases such as
the bubonic plague (transmitted by rat fleas) that decimated
over a quarter of the human population in Europe in the
Middle Ages, and more comprehensive disease surveys on
wild rats compared to wild mice.
Mammals in general are olfactory oriented; however,
the extensive research on scent marking and MHC discrim-
ination in mice may appear to suggest that olfactory cues
play a greater role in the social system of house mice than
rats. This difference is puzzling, and may reflect a bias in re-
search efforts. Indeed, recent genomic evidence shows that
rats have in fact 37% more genes and pseudogenes involved
in olfaction than mice, thus suggesting further avenues for
behavioral and physiological work.
This apparent discrepancy between behavioral and ge-
netic data also highlights a more general phenomenon; per-
haps more than any other mammalian species, our knowl-
edge of rats and mice reveals a tale of (at least) two cultures
in the biological sciences: broadly speaking, those who are
interested in animals for their own sake and those who are
interested in them as models for research related to human
concerns. These two approaches inevitably involve different
techniques and are currently separated by a barrier of jar-
gon and concepts. As a result, their relevance to each other
is underexploited: on the one hand, work in whole ani-
mal biology can help those that are interested in causal ex-
planations (mostly biomedical scientists). Although the lan-
guage of sociobiology, for example, has already proved a
useful metaphor for investigating intragenomic conflicts, it
is only recently that zoologists have been able to convince
biomedical scientists that an understanding of why animals
do what they do can assist in the design and interpreta-
tion of experimental work on these animals (e.g., appropri-
ate husbandry, objective interpretation of results, more ex-
ternal validity, increased statistical power). Because of their
ubiquitous use as laboratory animals, this is an example
where fundamental knowledge of basic evolutionary history
and biology can have applied benefits.
But the converse is equally true: biomedically driven lab-
oratory discoveries ranging from psychology to genetics
should be used by field biologists to understand better the
socioecology of a species. For example, although the rats’
ability to avoid ingesting poisons had been experienced by
rat catchers worldwide as an impediment to the success of
control programs (bait shyness), it was laboratory psychol-
ogists who demonstrated the existence of long delay learn-
ing, and the conditions under which it can be achieved (Gar-
cia et al. 1966; Garcia and Koelling 1966; Kalat and Rozin
1973). Similarly, the two main types of feeding patterns ob-
served by nutritional biologists in the laboratory (pre- and
postprandial correlations) provide insight into the physio-
logical mechanisms underlying feeding in mammals (Le
Magnen 1985) but can also be used to infer how animals
might feed in the wild, and provide testable predictions
about the constraints of social and environmental factors
on feeding (Berdoy 1994; Slater 1981). Finally, the recent
completion of the rat and mouse genomes will bring im-
portant insights into some aspects of rodent evolution of
interest to behavioral ecologists. As rats and mice tend, all
too often, to be tarred by the same brush, the genetic evi-
dence (contrary to initial expectation) actually emphasizes
the fact that, at least in terms of number of genes, there is as
much difference between mice and rats as there is between
rats and humans (see table 32.1). More specific compari-
sons between rats and mice also highlight that the genomic
regions that appear to have evolved fastest (those involved
in chemosensation, olfactory receptors, pheromones, cyto-
chromes P450, proteases, and protease inhibitors) are those
associated with special characteristics of the rats feeding be-
havior, social interaction, and reproduction. And these are
the very traits that fascinate us. The time is therefore ripe
for those interested in genetic societies (sensu Haig 1997)
and those interested in rodent societies to take a further
step toward each other.392 Chapter Thirty-Two