Abstract
Naked mole-rats (Heterocephalus glaber) are subterranean rodents that utilize their incisors for feeding, chisel-tooth digging of complex tunnel systems, social interactions, and defense in their eusocial colony structure. Previous studies have shown that naked mole-rats have morphological and anatomical adaptations that predict strong bite forces, namely, skulls that are relatively tall and wide, in addition to impressive masticatory musculature. However, no studies to date have directly measured bite force in this species or analyzed the relationship between bite force and social caste. In the current study, we assessed adult naked mole-rat maximum bite force in relation to body mass, in addition to considering each animal’s position within the eusocial hierarchy (i.e., dominant versus subordinate). Each animal was permitted to freely interact with a piezo-resistive bite force sensor. Our results showed that bite force was correlated with body mass in subordinate but not in dominant naked mole-rats, and that subordinate animals exhibited a shorter latency in producing their first bite. Maximum bite force was significantly influenced by caste. In comparing bite force with available data from previous studies across 82 additional mammalian species, subordinate naked mole-rats exhibited a bite force that was 65% higher than predicted for their body size, comparable to Tasmanian devils and exceeding bite force values for all of the carnivorans included for comparison. These results supported the hypothesis that the naked mole-rat’s bite force would exceed predictions based on body size due to the behavioral importance and specialization of the naked mole-rat incisors. This study provides insight into the differences in bite force across species, and the significant role that social and ecological factors might play in the evolutionary relationship between bite force performance and underlying anatomical structures.
Highlights
The maximum bite force across different taxa varies according to a wide range of factors including ecological niche, diet, and behavioral use of dentition
If food was offered in place of the probe at the tunnel’s terminal, the naked molerat would tear off parts of the food with its incisors and retreat backward through the tunnel to the larger housing chamber where it grasped the food between its forepaws to steady it during consumption
Naked mole-rats were assessed across multiple variables including bite frequency, bite latency, and maximum bite force in order to characterize their biting behaviors in relation to body mass and caste
Summary
The maximum bite force across different taxa varies according to a wide range of factors including ecological niche, diet, and behavioral use of dentition. Anatomical characteristics such as body mass have proven to be significant predictors of bite force (Wroe et al, 2005; Anderson et al, 2008; Freeman and Lemen, 2008a; Marshall et al, 2012). Strong bite force estimates based on cranial morphology have been shown for predators that rely on the ability to effectively incapacitate and dismember prey (Christiansen and Wroe, 2007). High bite force quotients (BFQs) (comparisons to predicted bite forces across a range of taxa with different body masses based on linear regression analyses) have been attributed to osteophages, tasked with breaking down bone material, as well as to herbivores that predominantly ingest geophytes and other hard vegetables (Herrel et al, 2002; Erickson et al, 2003; Herrel and O’Reilly, 2005; Wroe et al, 2005; Lappin et al, 2017)
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