Ecological conditions experienced by offspring during pregnancy and early post-natal life determine mandible size in roe deer

Abstract

Population dynamics studies and harvesting strategies often take advantage of body size measurements. Selected elements of the skeletal system such as mandibles, are often used as retrospective indices to describe body size. The variation in mandibular measurements reflects the variation in the ecological context and hence the variation in animal performance. We investigated the length of the anterior and posterior sections of the mandible in relation to the conditions experienced by juveniles of 8–10 months of age during prenatal and early postnatal life and we evaluated these parameters as ecological indicators of juvenile condition as well as female reproductive condition in a roe deer population living in the southern part of the species range. We analyzed a sample of over 24,000 mandibles of roe deer shot in 22 hunting districts in the Arezzo province (Tuscany, Central Italy) from 2005 to 2015 per age class. Mandible total length in juveniles is equal to 90% of total length in adults. In this stage of life the growing of the mandible’s anterior section is already completed while that of the posterior section is still ongoing. Environmental conditions conveyed by forest productivity, agricultural land use, local population density and climate strongly affected the growth of the anterior and posterior sections of the mandibles. Conditions experienced both by pregnant females and offspring played an important role in shaping the length of the anterior section, while the size of the posterior section was found to be related to the conditions experienced by offspring. Temporal changes of the length of the anterior section are a particularly suitable index of growth constraints. Anterior section length in fact differs according to more or less advantageous conditions recorded not only in the year of birth, but also in the previous year. Similarly, the sexual size dimorphism of the anterior section of the roe deer mandible can be used to describe the quality of females above two years of age, as well as habitat value. Hence the anterior section length of the mandible and its sexual size dimorphism are indexes that can provide cues of population performance, because they capture the system’s complexities, while remain simple enough to be easily and routinely used in the majority of European countries where roe deer hunting period extends from early autumn to late spring.

Sex‐specific impact of tooth wear on senescence in a low‐dimorphic mammal species: The European roe deer (Capreolus capreolus)

“…In the laboratory, measurements of mandibles and teeth were done with a digital calliper (±0.01 mm) always by the same researcher (see Table 1 for a description of collected measurements). For the analysed population, the mean lengths of mandible (ML), a proxy of skeletal size, for adult females and males were 155.4 and 158.0 mm, respectively (see De Marinis et al., 2019).…”

“…BW and BW/ML were related to tooth wear score in 212 adult males and compared to the mean value of eviscerated body mass and the body condition index of adult males in the same population (De Marinis et al., 2019; see Chirichella et al., 2021 for a comparison with adult females in the same population).…”

Dentition and body condition: tooth wear as a correlate of weight loss in roe deer

“…In the laboratory, the length of the mandible (ML ± 0.01 mm) was measured as a proxy of skeletal size with a digital caliper. ML was measured (always by the same researcher) from the anterior margin of the alveolus of the first incisor (I 1 ) to the posterior margin of the Processus angularis (see [ 56 ]). For the Arezzo province population, the mean value of ML for adult females was 156.7 mm (see [ 56 ]).…”

“…Eviscerated body mass and ratio of eviscerated body mass to total mandible length (i.e., BW/ML), as a proxy of body condition in roe deer [ 68 – 70 ], were related to the tooth wear score in 319 roe deer adult females, and compared to the mean value of eviscerated body mass and the body condition index for adult females of the same population [ 55 , 56 ].…”

Effects of forest management and roe deer impact on a mountain forest development in the Italian Apennines: A modelling approach using LANDIS-II

“…Four ungulate species are present in the study area, two are widely abundant, roe deer and wild boar ( Sus scrofa ), while the others, red deer and fallow deer ( Cervus elaphus and Dama dama ) are locally abundant but more dispersed. Only roe deer has been considered in the modelling being the most abundant ubiquitous deer species (density consistently higher than 12 individuals per square kilometre, [44]). Two predators are present in the area, wolf ( Canis lupus ) and red fox ( Vulpes vulpes ).…”