Influence of captivity and selection on limb long bone cross‐sectional morphology of reindeer

Abstract

The emergence of pastoralism and animal husbandry has been a critical point in the history of human evolution. Beyond profound behavioural changes in domesticated animals compared to wild ones, characterising the morphological changes associated with domestication process remains challenging. Because reindeer (Rangifer tarandus) can be considered to still be in the early phases of the domestication process, the study of modern populations provides a unique opportunity to examine the impact of captivity and selective breeding on skeletal changes. In this work, we investigated the morphological changes in long limb bone cross‐sections using 137 wild and domestic reindeer individuals bred in free‐range, in captivity or used for racing and pulling. The shape and shaft cortical thickness of the six long limb bones (i.e., humerus, radioulna, metacarpal, femur, tibia and metatarsal) were measured using a 2D‐geometric morphometrics approach taking into account subspecies, sex, body mass and lifestyle differences. These bones are important to understanding functional morphological changes because they can provide information on feeding and locomotor behaviours, as well as on body propulsion and weight bearing. Apart from the effects of taxonomy, etho‐ecology and sex, we have found that captivity and selection induced important variations in the size and body mass of modern reindeer. Our results also showed that patterns of variation in cortical bone thickness of long limb bone cross‐sections were strongly impacted by body mass and human‐imposed restrictions in roaming. This demonstrates that bone cross‐sections can provide information on changes in locomotor, reproductive and feeding behaviours induced by the domestication process. These results are valuable not only for (paleo) biologists studying the impact of captivity and selection in ungulates but also for archaeologists exploring the origins of domestication and early herding strategies.

Paleopathology, Entheseal Changes, and Cross-Sectional Geometry: The Zooarchaeology of Working Animals

“…Niinimäki and Salmi (2021) explored the covariation in reindeer by analyzing the cross-sections and EC of 50 wild forest, domesticated free-range, and zoo reindeer. They found that bone formation on almost every examined enthesis was positively associated with CSBG values, further establishing their relationship from previous studies on humans (Niinimäki and Salmi 2021;Pelletier, Niinimäki, and Salmi 2021). Additionally, they found that entheses on the humerus effectively separated different groups of reindeer based on activity levels that size nor age could entirely account for, implying activity as a possible underlying factor causing these observations (Niinimäki and Salmi 2021;Salmi, Niinimäki, and Pudas 2020).…”

“…In animals, a cross-sectional study has also shown direct associations between bone plasticity and its response to human-controlled activities in donkeys (Shackelford, Marshall, and Peters 2013). In addition, new research on types of human-raised and wild reindeer populations in the North has extended the use of CSBG methods to not only evaluate the efficacy of EC scoring methods (Niinimäki and Salmi 2021) but to demonstrate its potential as a valuable indicator of changes in humananimal relations over time (Pelletier Niinimäki, and Salmi 2021).…”

“…They found non-working reindeer and free-ranging reindeer (captive during the winter) had increased body mass, decreased body size, and thicker cortical cross-sections than wild reindeer. The authors attributed this to differences in feeding and locomotion behaviour, such as wild reindeer foraging through the snow for lichen or captive reindeer requiring more body support for standing still for long periods (Pelletier, Niinimäki, and Salmi 2021;Niinimäki and Salmi 2016;Hull, Niinimäki, and Salmi 2020). This behaviour typically begins in adolescence, when bone growth is the most susceptible to activity (Jurmain et al, 2012;Niinimäki andPathways 3 (2022) 52-70 Salmi, 2021).…”

Size and shape of the semicircular canal of the inner ear: A new marker of pig domestication?

“…Unfortunately, any adaptive or functional explanations for the differences in semicircular canal shape would be highly speculative. It might be tempting to propose an explanation linked to the locomotor changes of the animals during domestication and captivity known to have impacted the skeleton (e.g., Harbers, Neaux, et al, 2020 ; Harbers, Zanolli, et al, 2020 ; Pelletier et al, 2020 ; Pelletier et al, 2021 ), but it is just as possible that the changes in skull morphology (Evin et al, 2017 ; Owen et al, 2014b ) led to changes of the inner ear, or that drift was also involved.…”

The Archaeology of Reindeer Domestication and Herding Practices in Northern Fennoscandia

“…Although reindeer have never been kept in complete captivity, apart from zoo-kept individuals, practices such as parttime penning and other human-influenced changes in reindeer mobility patterns may cause skeletal morphology changes. There also are other functional changes such as working that affect skeletal morphology: Bone cross-sectional properties differ between working and non-working reindeer; and working reindeer also tend to be larger and more robust than non-working reindeer, although the latter is a product of the selection of suitable individuals for training, not domestication-related selection pressure (Niinimäki et al 2021;Pelletier et al 2020Pelletier et al , 2021b.…”