Spatiotemporal variations in antler development among two neighbouring, yet isolated, red deer populations

Abstract: Whereas wildlife occurring in fragmented landscapes is frequently the subject of genetic investigation, there has been relatively little attention for associated spatiotemporal variations in phenotypic traits. For example, many studies have reported the genetic variation and structure of present day red deer (Cervus elaphus elaphus) – showing both hybridization with other Cervus species and fragmentation – but the consequences for phenotypic traits, even when as conspicuous and elastic as antler size, have not been considered. To examine fine-scale differences in a phenotypic trait in large wildlife species inhabiting fragmented landscapes, we analyzed the antlers of red deer from two neighbouring populations occurring in the Netherlands. To test for area and drought effects, we quantified antler mass, burr circumference and the number of tines from antler series shed in the years 2011 to 2020 by 25 stags of the population at the Hoge Veluwe Estate (n=20) and the relict population at Planken Wambuis (n=5). We found that red deer from the Hoge Veluwe have significantly heavier and larger antlers with more tines (average mass: 3.0 kg; average burr circumference: 23.0 cm, average number of tines: ten) than deer from the neighbouring relict population from Planken Wambuis (2.3 kg, 21.5 cm and eight tines, respectively). Despite the provision of drinking water and pasture management within the Hoge Veluwe, antler development appeared to be significantly diminished by the summer drought of 2018, but only in mature stags (males aged seven years and older). We thus found, on the one hand, a naturally induced variation in a phenotypic trait, despite wildlife management aimed at relaxing natural stressors. On the other hand, the considerable phenotypic variation detected at a small spatial scale illustrated strong anthropogenic influence: it appears that wildlife populations in fragmented landscapes are not only affected genetically, but also phenotypically. We conclude that in fragmented landscapes, deer antlers – and perhaps phenotypic traits of wildlife in general – are strongly shaped by anthropogenic influences, but that naturally induced variation is not completely erased.