The bone collector: temporal patterns of bone-gnawing behaviour define osteophagia as a female prerogative in a large rodent

Abstract

Calcium and phosphorous consumption is essential for bone development and maintenance throughout life, particularly to pregnant and lactating females. Bone consumption may provide mothers with the required supplemental amount of calcium and phosphorous. Osteophagia has been reported in a number of herbivore species as supplying such key mineral elements, although sound evidence is lacking for rodents. The diet of the crested porcupine is vegetarian and predominantly composed by roots and hypogeal storage organs. Gnawed bone residuals have often been observed in the surroundings of porcupine setts. This behaviour may have evolved to reduce the indefinite growth of incisor teeth, to increase calcium and phosphorous supply, or to fulfil both these functions. To clarify this issue, five setts were monitored for 3 years and bones in front of sett entries were counted and collected once a month. A total of 63 bones (mainly femurs and shins: 38.8%) was detected, mainly belonging to wild (46.03%) and domestic (28.57%) ungulates. The presence of gnawed bones in front of sett entries was recorded throughout the year, with a peak at the start of February. Camera-trapping data confirmed that areas surroundings house-farms, where most bones were probably collected, were only selected in the cold season. The peak of gnawed bone detection overlapped with the birth peak, suggesting that bones may be consumed by lactating females to increase the amount of minerals in their diet. This suggestion was further confirmed by the detection of no gnawed bones in front of the sett of the male-male pair. Porcupines are known to collect and gnaw bones in the surroundings of their setts, but ecological explanations and temporal patterns of this behaviour are unknown. We monitored five setts for 3 years, measuring and identifying gnawed bones in front of sett entries once a month. We then conducted an intensive camera-trapping session to monitor areas surrounding house-farms. Bone collection occurred throughout the year, with a peak in February, coinciding with the birth peak of this species. We therefore suggested that bone consumption could be a female prerogative, related to a supply of minerals in diet, as no gnawed bone was observed at the sett of a male-male pair.