Abstract
The inhibition of infanticide can be considered a prerequisite for the onset of paternal behavior. Thus, hormones such as testosterone (T) would be expected to mediate the inhibition of aggression toward pups and the onset of paternal care. However, the effect of T in onset of this behavior seems to depend of sexual experience. The aim of this study was to determine whether T induces paternal behavior in sexually inexperienced males of the Mexican volcano mouse (Neotomodon alstoni). For this, 33 non-paternal males were selected based on paternal behavior tests. These non-paternal mice were organized in three groups: 10 males were castrated, 10 subjected to sham procedure, and 13 underwent castration and T replacement. After of these treatments, the males were again evaluated by a second paternal behavior test, and blood samples were obtained to measure plasma T levels by radioimmunoassay. Castrated males with T replacement changed their behavior; 46.2 % of these males displayed paternal behavior despite 92.3 % of these males having previously displayed aggressive behavior in the selection test. An increase in T facilitates the onset of paternal behavior in sexually inexperienced males of Mexican volcano mouse, as occurs in sexual experience males. These results support the hypothesis that an increase in T levels would be involved in the neuroendocrine mechanisms that suppress infanticide and promote the onset of parental behavior in Mexican volcano mice males. Future studies in this mouse will investigate whether T regulates the onset of paternal behavior via conversion to estradiol or whether both T metabolites are involved in its onset.
Highlights
Just as in females, males must inhibit their infanticidal behavior and become paternal before the birth of the pups to avoid hurting their own offspring
Castration did not have any effect on the behavior of sexually inexperienced male Mexican volcano mice; i.e., the percentage of mice that behaved aggressively toward pups before and after this treatment was the same (Table 1)
Castrated and sham-operated males did not display any significant change in their behavior toward pups, but 46.2 % of sexually inexperienced, castrated males treated with T replacement therapy exhibited paternal behavior despite being indifferent toward pups or displaying infanticidal behavior before treatment
Summary
Males must inhibit their infanticidal behavior and become paternal before the birth of the pups to avoid hurting their own offspring In the California mouse (Peromyscus californicus), T has been demonstrated to promote paternal care in sexually experienced males, whereas castration reduces paternal care (Trainor & Marler, 2001) In rodents such as the dwarf hamster, castration significantly reduces T concentration, paternal behavior is not affected (Hume & Wynne-Edwards, 2005). Trainor and Marler (2002) have indicated that conflicting results of different studies regarding the role of T in paternal behavior, may be explained by the inclusion of sexually inexperienced males, because copulation is a factor that facilitates paternal care In this rodent a positive correlation between T levels and the amount of paternal care was observed five days after birth (Luis et al 2009). The aim of this study was to determine whether T induces paternal behavior in sexually inexperienced males of the Mexican volcano mouse (Neotomodon alstoni)
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