Kalahari vulture declines, through the eyes of meerkats^§

Vulture populations are experiencing rapid declines across the globe. While the declines have been most precipitous in Asia, recent reports suggest African populations are likewise imminently threatened. As the factors underlying these general population trends are multifaceted and will vary in their relative intensity spatially, it is imperative that monitoring data across different vulture populations is assimilated if targeted conservation action is to prove most effective. In this study, we highlight a medium-term decline in the African White-backed Vulture $\textit{Gyps africanus}$ population inhabiting the southern Kalahari, South Africa, using a long-term behavioural data set collected from a habituated population of meerkats $\textit{Suricata suricatta}$. Meerkats emit an alarm call on sighting airborne vultures, which elicits a group-level response, such that the rates at which this behaviour is recorded in meerkats provides a high-resolution proxy for local vulture abundance. Although unconventional, this sampling method uncovered a steady decline over 17 years in White-backed Vulture numbers that mirrors the temporal decline recently documented in other southern African populations. Tout autour du globe, les populations de vautours connaissent un déclin rapide. Alors que ce déclin s’est précipité au sein des populations d’Asie, de récents rapports suggèrent que les populations africaines sont au moins aussi menacées à court terme. Les facteurs qui influencent ces tendances démographiques générales ont plusieurs facettes et varient de manière spatiale dans leur intensité relative. Par conséquent, il est impératif de collecter et regrouper des données de surveillance sur différentes populations pour mettre en place des stratégies de conservation efficaces et ciblées. Dans cette étude, je souligne le déclin à moyen terme d’une population de Vautour africain ($\textit{Gyps africanus}$) vivant dans la partie sud du Kalahari, en Afrique du Sud, en utilisant un jeu de données comportementales de long terme, récoltées sur une population de suricates ($\textit{Suricata suricatta}$) habitués. Les suricates émettent une vocalisation d’alarme lorsqu’ils voient un vautour en vol, ce qui déclenche une réponse anti-prédateur au sein du groupe. La fréquence à laquelle ce comportement est observé et relevé chez les suricates représente un substitut fiable et de grande résolution pour attester de l’abondance locale de vautours. Bien que peu conventionnelle, cette méthode d’échantillonnage a mis en évidence une diminution constante du nombre de Vautours africains au cours de 17 dernières années, qui reflète le déclin récemment documenté dans d’autres populations d’Afrique australe.This paper has relied on the longitudinal behavioural data of the Kalahari Meerkat Project, which is currently supported by the European Research Council (Research Grant no. 294494 to TCB since July 2012), the Mammal Research Institute at the University of Pretoria, and the University of Zurich. JBT is funded by a NERC Doctoral Training Program

The importance of being beta: female succession in a cooperative breeder

In singular cooperative breeders few females breed successfully, but those that acquire dominant positions can achieve high levels of breeding success, leading to strong selection for traits that enable individuals to acquire and maintain dominance status. However, little is known about the process by which females acquire dominant breeding status or the traits that enable them to do so. Female meerkats, Suricata suricatta, can acquire dominance either by inheritance after the death of the previous dominant, by displacing the incumbent dominant or at the foundation of a new group. Here we investigated the possible fitness benefits associated with these different routes to dominance and the traits that affect an individual's probability of acquiring dominance via these routes. We found that all routes to dominance had similar fitness benefits and that when a dominance vacancy arose, weight was the main determinate of succession, with age still influencing within-group succession and the eldest subordinate female, the beta, often succeeding to dominance. Since the chance that subordinate females will acquire dominance is also positively correlated with the duration of their tenure in the beta position, we tested whether beta females adjusted their growth or cooperative behaviour to avoid eviction and increased their tenure length as the beta. However, there was no indication that betas employed either strategy to increase their tenure. Given that the differing routes to dominance have equivalent fitness pay-offs and are triggered stochastically, selection probably favours flexibility rather than strategies that commit individuals to a specific route.The Kalahari Meerkat Project was funded by the European Research Council (grant no. 294494), the Natural Environment Research Council (grant no. NE/G006822/1) and the Swiss National Science Foundation and supported by the Universities of Cambridge, Zurich and Pretoria

Cortisol levels are positively associated with pup-feeding rates in male meerkats

In societies of cooperative vertebrates, individual differences in contributions to offspring care are commonly substantial. Recent attempts to explain the causes of this variation have focused on correlations between contributions to care and the protein hormone prolactin, or the steroid hormone testosterone. However, such studies have seldom considered the importance of other hormones or controlled for non-hormonal factors that are correlative with both individual hormone levels and contributions to care. Using multivariate statistics, we show that hormone levels explain significant variation in contributions to pup-feeding by male meerkats, even after controlling for non-hormonal effects. However, long-term contributions to pup provisioning were significantly and positively correlated with plasma levels of cortisol rather than prolactin, while plasma levels of testosterone were not related to individual patterns of pup-feeding. Furthermore, a playback experiment that used pup begging calls to increase the feeding rates of male helpers gave rise to parallel increases in plasma cortisol levels, whilst prolactin and testosterone levels remained unchanged. Our findings confirm that hormones can explain significant amounts of variation in contributions to offspring feeding, and that cortisol, not prolactin, is the hormone most strongly associated with pup-feeding in cooperative male meerkats

Effects of early-life competition and maternal nutrition on telomere lengths in wild meerkats

Early-life adversity can affect health, survival and fitness later in life, and recent evidence suggests that telomere attrition may link early conditions with their delayed consequences. Here, we investigate the link between early-life competition and telomere length in wild meerkats. Our results show that, when multiple females breed concurrently, increases in the number of pups in the group are associated with shorter telomeres in pups. Given that pups from different litters compete for access to milk, we tested whether this effect is due to nutritional constraints on maternal milk production, by experimentally supplementing females’ diets during gestation and lactation. While control pups facing high competition had shorter telomeres, the negative effects of pup number on telomere lengths were absent when maternal nutrition was experimentally improved. Shortened pup telomeres were associated with reduced survival to adulthood, suggesting that early-life competition for nutrition has detrimental fitness consequences that are reflected in telomere lengths. Dominant females commonly kill pups born to subordinates, thereby reducing competition and increasing growth rates of their own pups. Our work suggests an additional benefit of infanticide may be that it also reduces telomere shortening caused by competition for resources, with associated benefits for offspring ageing profiles and longevity.The Kalahari Meerkat Project is supported by the Universities of Cambridge, Zurich and Pretoria. Components of this research were supported by grants to TC-B from the Natural Environment Research Council (grant no. NE/G006822/1) and the European Research Council (grant no. 294494). PM was supported by the European Research Council (grant no. 268926)

Climate and the distribution of cooperative breeding in mammals

Cooperative breeding systems, in which non-breeding individuals provide care for the offspring of dominant group members, occur in less than 1% of mammals and are associated with social monogamy and the production of multiple offspring per birth (polytocy). Here, we show that the distribution of alloparental care by non-breeding subordinates is associated with habitats where annual rainfall is low. A possible reason for this association is that the females of species found in arid environments are usually polytocous and this may have facilitated the evolution of alloparental care.This project was funded by the European Research Commission (grant no. 294494-THCB2011)

The effects of recruitment to direct predator cues on predator responses in meerkats

Behavioral responses of animals to direct predator cues (DPCs; e.g., urine) are common and may improve their survival. We investigated wild meerkat (Suricata suricatta) responses to DPCs by taking an experimental approach. When meerkats encounter a DPC they often recruit group members by emitting a call type, which causes the group members to interrupt foraging and approach the caller. The aim of this study was to identify the qualities of olfactory predator cues, which affect the strength of response by meerkats, and determine the benefits of responses to such cues. Experimental exposure to dog (Canis lupus) urine as a DPC revealed that the recruited individuals increased vigilance to fresh urine in comparison to older urine, whereas a higher quantity of urine did not induce such an effect. Both freshness and higher quantities increased the proportion of group members recruited. These results indicate that recruitment might play a crucial role in correctly assessing the current level of danger and that recruiting might facilitate group decision making. To test the prediction that the reaction to a DPC enhances early predator response, we presented a DPC of a predator and a control cue of a herbivore, and each time simultaneously moved a full-mounted caracal (Caracal caracal) in the vicinity of the group. Meerkats responded earlier to the caracal when the DPC was presented, indicating that the response to a DPC facilitates predator response and that they use information from the cue that reliably reflects the risk in the current momen

Failure of retrograde cerebral perfusion to attenuate metabolic changes associated with hypothermic circulatory arrest

AbstractObjectives: Although retrograde cerebral perfusion has become a popular adjunctive technique and may improve cerebral ischemic tolerance during hypothermic circulatory arrest, direct cerebral metabolic benefit has yet to be demonstrated in human subjects. We investigated the post-arrest metabolic phenomena with and without retrograde cerebral perfusion in patients. Methods: In a prospective randomized trial, 42 patients undergoing aortic surgery requiring hypothermic circulatory arrest were allocated to receive hypothermic circulatory arrest alone (n = 21) or hypothermic circulatory arrest with additional retrograde cerebral perfusion (n = 21). Circulatory arrest was commenced at 15°C, and retrograde perfusion was instituted through the superior vena cava at a maximum jugular bulb pressure of 25 mm Hg. Transcranial, paired, repeated samples of the arterial and jugular bulb blood were analyzed for oxygen and glucose. Velocity in the right middle cerebral artery was also measured simultaneously. Results: There were 3 (7.1%) deaths and 3 (7.1%) episodes of neurologic deficit. Mean bypass and circulatory arrest duration (in minutes) were similar between groups (P = .4 and .14). The mean retrograde perfusion duration was 23 minutes. Post-arrest nasopharyngeal temperature was similar (15.3°C vs 15.3°C). Retrograde perfusion did not affect post-arrest oxygen extraction, glucose extraction, or jugular bulb Po2. There was no immediate lactate release immediately after hypothermic circulatory arrest. Conclusions: Retrograde cerebral perfusion did not influence immediate post-arrest nasopharyngeal temperature or cerebral metabolic recovery. The low jugular bulb Po2 suggests equivalent ischemia. These findings cast doubt on the effectiveness of retrograde cerebral perfusion as a metabolic adjunct to hypothermic circulatory arrest.J Thorac Cardiovasc Surg. 2002;123:943-50