Low effective mechanical advantage of giraffes' limbs during walking reveals trade-off between limb length and locomotor performance.

Giraffes (Giraffa camelopardalis) possess specialized locomotor morphology, namely elongate and gracile distal limbs. While this contributes to their overall height and enhances feeding behavior, we propose that the combination of long limb segments and modest muscle lever arms results in low effective mechanical advantage (EMA, the ratio of in-lever to out-lever moment arms), when compared with other cursorial mammals. To test this, we used a combination of experimentally measured kinematics and ground reaction forces (GRFs), musculoskeletal modeling, and inverse dynamics to calculate giraffe forelimb EMA during walking. Giraffes walk with an EMA of 0.34 (±0.05 SD), with no evident association with speed within their walking gait. Giraffe EMA was about four times lower than expectations extrapolated from other mammals, ranging from 0.03 to 297 kg, and this provides further evidence that EMA plateaus or even diminishes in mammals exceeding horse size. We further tested the idea that limb segment length is a factor which determines EMA, by modeling the GRF and muscle moment arms in the extinct giraffid Sivatherium giganteum and the other extant giraffid, Okapia johnstoni. Giraffa and Okapia shared similar EMA, despite a four to sixfold difference in body mass (Okapia EMA = 0.38). In contrast, Sivatherium, sharing a similar body mass with Giraffa, had greater EMA (0.59), which we propose reflects behavioral differences, such as a somewhat increased capability for athletic performance. Our modeling approach suggests that limb length is a determinant of GRF moment arm magnitude and that unless muscle moment arms scale isometrically with limb length, tall mammals are prone to low EMA.

Effects of browsing enrichment associated with the temperature-humidity index and landscaping trees in giraffes (Giraffa camelopardalisreticulata).

Enclosure environments for captive giraffes can be improved by promoting species-specific behaviors and extending foraging behavior. To date, however, the effects of climatic (temperature-humidity index, THI) and environmental factors (landscaping trees) on the enrichment of captive settings have not been studied. Therefore, the present study explored the effects of browsing enrichment on the licking behavior of captive giraffes. From May 2019 to February 2020, three giraffes in the Kyoto City Zoo, Japan, were observed for 270 h over two consecutive seasons (pre- and post-deciduous). Overall, branch foraging behavior and licking behavior were weakly and negatively correlated. In the pre-deciduous period, THI was significantly and negatively correlated with giraffe activity, and some individuals exhibited significantly reduced foraging behavior. Therefore, browsing enrichment under extreme heat may not improve giraffe rearing environments. Moreover, in the post-deciduous period, with decreased availability of leaves on landscaping trees, the non-branch foraging behavior of giraffes was significantly increased, with a corresponding significant increase in licking behavior. Therefore, landscaping trees affect the foraging behavior of captive giraffes.

A comparative perspective on the evolution of mammalian reactions to dead conspecifics.

In a variety of mammalian species, mothers and others care for and/or carry deceased newborns, and sometimes other conspecifics. The rationale for such behavior remains elusive. Based upon field observations of olive baboon (Papio anubis), African elephant (Loxodonta africana), and Thornicroft's giraffe (Giraffa camelopardalis) responses to recently dead conspecifics, combined with reports in the literature, a hypothesis is proposed to account for this activity. Among female mammals, lifetime reproductive success is more dependent upon rearing, than production, of offspring. The successful nurturing of progeny is associated with a strong maternal-offspring bond. One of the most important chemicals involved in both lactation and mother-infant bonding is oxytocin, a tiny molecule that has a lengthy evolutionary history and is implicated in the formation of social bonds across mammals. Evolution has extended the impact of oxytocin by adopting it beyond the original mother-infant bond to the establishment of social bonds that are required among group-living animals. Hence, sociality is a consequence of the same fundamental biological mediator of mother-offspring bonding, and this intricate connection between physiology and behavior has produced a situation where sometimes animals will care for or carry dead companions. Ways to test this hypothesis, as well as a potential way to refute it, are proposed.

Training giraffe (Giraffa camelopardalis reticulata) for front foot radiographs and hoof care.

For a large herd of reticulated giraffes, a mainly operant-based training program was created for front foot radiographs and hoof trims in an effort to diagnose and better manage lameness. Behaviors were shaped in a restricted contact set-up, using a positive reinforcement procedure to teach a series of mastered cued behaviors. This training was used to obtain lateral and lateral oblique front foot radiographs for the entire herd. Radiographs were diagnostic for multiple possible causes of lameness including fractures and osteitis of the distal phalangeal bone, hoof overgrowth, osteoarthritis of the distal interphalangeal joint, rotation of the distal phalangeal bone, sesamoid bone cysts, and sole foreign bodies. By training giraffe for foot radiographs and hoof trims, potential causes of lameness could be identified and better managed. Long-term, the results may help zoos identify best practices for managing and preventing lameness in giraffe. Zoo Biol. 35:228-236, 2016. © 2016 Wiley Periodicals, Inc.

A Multi-Institutional Assessment of Factors Influencing Locomotion and Pacing in Captive Okapis (Okapia johnstoni).

The okapi (Okapia johnstoni), native to the Democratic Republic of Congo, is a large, solitary, and diurnal forest-dwelling ungulate highly sensitive to captive conditions. The captive population demonstrates persistent health problems, reproductive abnormalities, and several potentially abnormal repetitive behaviors. This study reports on locomotion and pacing in adult male and female okapis. Commonly, data on repetitive behavior have been derived from surveys. Although insightful, the results are often highly generalized and provide little information about the true preponderance and nature of such behavior in a population. In this study, direct observations determining how often and when a behavior of interest occurs are paired with information on factors (intrinsic and extrinsic) that can impact a nonhuman animal's propensity to perform repetitive behavior. More than half of the North American okapi population comprised the study population. Each animal was studied for 2 summer and winter seasons. Factors predictive of pacing in both males and females included 3 housing and habitat factors and 4 management factors. Patterns of locomotion and the rate and pattern of pacing in males when compared with females suggested different mechanisms may be driving these behaviors in the different sexes and that a sex-specific management strategy would benefit this species.

The first description of dominance hierarchy in captive giraffe: not loose and egalitarian, but clear and linear.

Wild giraffes live in extensive groups in the fission fusion system, maintaining long social distances and loose social bonds. Within these groups, resources are widely distributed, agonistic encounters are scarce and the dominance hierarchy was reported in males only, while never deeply analysed. In captivity, the possibility to maintain inter-individual distances is limited and part of the resources is not evenly distributed. Consequently, we suggest that agonistic encounters should be more frequent, leading to the establishment of the dominance hierarchy. Based on the differences in resource-holding potential, we suggested that the rank of an individual would be affected by age and sex. Based on hypotheses of prior ownership, we tested whether rank was positively affected by the time spent in a herd and whether it was stable in adult females, which were present long-term in the same herd. We originally monitored four herds of Rothschild giraffes (Giraffa camelopardalis rothschildii) in Dvur Králové zoo (n = 8), Liberec zoo (n = 6), and two herds in Prague zoo: Prague 1 (n = 8) and Prague 2 (n = 9). The Prague 1 and Prague 2 herds were then combined and the resulting fifth herd was observed over three consecutive years (2009, 2010, and 2011) (n = 14, 13, and 14, respectively). We revealed a significantly linear hierarchy in Dvur Králové, Prague 2 and in the combined herd in Prague. Rank was significantly affected by age in all herds; older individuals dominated the younger ones. In females, rank was positively affected by the time spent in the herd and adult females in Prague maintained their rank during three consecutive years. This study represents the first analysis of the dominance hierarchy in the captive giraffe, and discusses the behavioural flexibility of the social structure in response to monopolisable resources in a captive environment.