A. Gottreich et al., Noninvolvement of testosterone in aggressive defense behavior in the male blind mole rat Spalax ehrenbergi, AGGR BEHAV, 27(1), 2001, pp. 64-72
Blind mole rats (Spalax ehrenbergi) are solitary and aggressive subterranea
n rodents, Aggressive defense behavior in the mole rat functions to deter n
eighboring competitors from territory, food, and mates and includes seismic
and odor signals. The aim of the present study was to determine whether th
e aggressive defense behavior displayed by male mole rats is testosterone d
ependent. Five behavioral variables were taken as being representative of s
uch aggressive interaction: exposing teeth, biting, bulldozing movements of
the head, soil blocking, and self-grooming. We monitored male testosterone
Levels and aggressiveness throughout the annual cycle, which can be divide
d into three main climatic periods: cold and rainy (September-February); wa
rm, during which the soil is still moist and easily excavated (March-May);
and hot (June-August), when the soil is hard and dry. In a second experimen
t the effect of endogenous and exogenous testosterone on male aggressive de
fense behavior was determined before and after castration and following tes
tosterone propionate replacement. We found fluctuations in male testosteron
e concentrations, with three peaks: in November, May, and August, one in ea
ch of the three climatic periods. However, these fluctuations did not corre
late with male aggressive behavior, which remained constant throughout the
year. Furthermore, because neither castration nor testosterone propionate r
eplacement in castrated individuals affected their defense behavior, we sug
gest that such behavior in male mole rats is testosterone independent. The
continuous excavation and maintenance of the mole rat's underground tunnel
system demands high energy expenditure year-round and constant defense of t
erritory sites and food caches from intraspecific rivals. Thus, although te
stosterone may fluctuate as a result of seasonal breeding cycles, constant
high levels of aggressive defense throughout the year are crucial for the s
urvival of the male mole rat in its solitary subterranean environment. (C)
2001 Wiley-Liss. Inc.