Biting forces in the subterranean rodent Ctenomys talarum (Caviomorpha: Octodontoidea)

FEDERICO BECERRA; ALEJANDRA ISABEL ECHEVERRÍA; ALDO IVÁN VASSALLO; ADRIÀ I. CASINOS

Mendoza, Argentina

Congreso; 10th Mammalogical Congress; 2009

IADIZA

Ctenomys talarum  is a Southamerican, subterranean and territorial rodent that digs using both forelimbs and incisors, the later being used when animals should confront hard soils, fibrous roots, or rocks. In this poligynous rodent the incisors are also used during inter male aggressive encounter for territory defense and access to females. On 20 wild females and 17 wild males (both adult and young individuals) caught at Mar de Cobo, Buenos Aires, Argentina, biting forces were measured using a Necco force transducer. Biting force was significantly greater in adult males than females (32 N vs. 28 N respectively; F=5.06; P<0.03). The greater value was registered in an adult male weighting 175 g and was of 41 N, nearly 24 times its body weight. A multiple regression analysis using as predictor variables several exosomatic measurements (body mass; body length; head length; skull height; mandibular width) showed that mandibular width –an indicator of masseteric muscles development– has a significant influence on biting force. In regressions against body mass, biting force scaled with an allometric coefficient of 0.88 [±0.13] in females and 0.97 [±0.12] in males. Non-significant differences were observed neither in the slope nor y-intercept of both sexes equations; therefore intersexual differences in biting forces observed in adults should mainly due to size dimorphism, since muscle force is proportional to muscle mass, and muscle mass is more or less isometric to body mass. Taken into account that soil hardness of the habitats occupied by C. talarum averages 100 N/cm2, and that incisor’s cross section in this tuco-tuco is about 0.1 cm2, it can be observed that the forces exerted by jaw adductor muscles at the level of the incisors is three times greater than that required for soil penetration.