Sexually selected sentinels? Evidence of a role for intrasexual competition in sentinel behavior

Walker, Lindsay A.; York, Jenny E.; Young, Andrew J.

doi:10.1093/beheco/arw064

Cited by 24 publications

(33 citation statements)

References 49 publications

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“…Young). Reproduction within the group is monopolized by a single dominant pair (Harrison, York, Cram, Hares, et al, ; Harrison, York, Cram, & Young, ) while subordinate group members contribute to a range of cooperative activities including feeding nestlings (Cram, Blount, & Young, ; Walker, York, & Young, ). Throughout the breeding season (October to April inclusive), all nests were closely monitored to attain lay and hatch dates for all eggs.…”

Section: Methodsmentioning

confidence: 99%

Telomere attrition predicts reduced survival in a wild social bird, but short telomeres do not

Wood

Young

2019

Molecular Ecology

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Attempts to understand the causes of variation in senescence trajectories would benefit greatly from biomarkers that reflect the progressive declines in somatic integrity (SI) that lead to senescence. While telomere length has attracted considerable interest in this regard, sources of variation in telomere length potentially unrelated to declines in SI could, in some contexts, leave telomere attrition rates a more effective biomarker than telomere length alone. Here, we investigate whether telomere length and telomere attrition rates predict the survival of wild white‐browed sparrow‐weaver nestlings (Plocepasser mahali). Our analyses of telomere length reveal counterintuitive patterns: telomere length soon after hatching negatively predicted nestling survival to fledging, a pattern that appears to be driven by differentially high in‐nest predation of broods with longer telomeres. Telomere length did not predict survival outside this period: neither hatchling telomere length nor telomere length in the mid‐nestling period predicted survival from fledging to adulthood. Our analyses using within‐individual telomere attrition rates, by contrast, revealed the expected relationships: nestlings that experienced a higher rate of telomere attrition were less likely to survive to adulthood, regardless of their initial telomere length and independent of effects of body mass. Our findings support the growing use of telomeric traits as biomarkers of SI, but lend strength to the view that longitudinal assessments of within‐individual telomere attrition since early life may be a more effective biomarker in some contexts than telomere length alone.

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Section: Methodsmentioning

confidence: 99%

Telomere attrition predicts reduced survival in a wild social bird, but short telomeres do not

Wood

Young

2019

Molecular Ecology

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“…Animal sentinel behaviour has been widely studied in many species of mammals, birds and even fish (reviewed by [15]). As can be imagined, many of them are cooperative breeders, such as jungle babblers, Turdoides striatus [1], pied babblers, Turdoides bicolor , [16,17], Arabian babblers, Turdoides squamiceps [5], Florida scrub jays, Aphelocoma coerulescens [4], white-browed sparrow weavers, Plocepasser mahali [18,19], dwarf mongooses, Helogala parvula [2,14] and meerkats, Suricata suricatta [20]. …”

Section: Introductionmentioning

confidence: 99%

“…In the pied babbler, the time is about 30% [16]. White-browed sparrow weaver groups have a sentinel about 21% of the time [19]. In the Florida scrub jay, groups were guarded by at least one sentinel about 33% in late summer, 50% in spring and about 75% in winter [4].…”

Section: Introductionmentioning

confidence: 99%

The sentinel behaviour of Arabian babbler floaters

Ostreiher

Heifetz

2017

R. Soc. open sci.

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The sentinel behaviour of 38 Arabian babbler adult floaters, who lived alone within a territory belonging to a foreign group, was studied and compared with their own sentinel behaviour in the past, when they were group members. All floaters acted as sentinels and uttered ‘alarm calls’. This suggests that sentinel activity is due at least, in part, to selfish motives. Floaters sentinelled less than they did as group members, with the decrease in sentinel activity sharper for ex-dominants than for ex-subordinates. One possible explanation for these differences is that sentinel activity is aimed not only at detecting predators, but also at detecting foreign conspecifics. Within a group, the latter incentive is stronger for breeding dominants than for subordinates, whereas all floaters alike may be trying to detect the owners of the territory in which they were roaming but also to avoid being detected by them. Other possible explanations are that floaters have less time and energy for sentinel activity because they are weaker or because foraging is more difficult in a foreign territory. This may be especially so for dominants who used to enjoy privileged access to food in their group. No significant difference was found in the rate of sentinels' ‘alarm calls’ between floaters and group members, suggesting that their main purpose is predator–prey communication, of which warning groupmates may be a side benefit.

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“…Previous studies compared sentinel durations of dominants and subordinates in cooperative breeders. In the Arabian babbler, Turdoides squamiceps (Wright, Berg, Kort, Khazin, & Maklakov, 2001a;Wright et al, 2001b), Florida scrub-jay, Aphelocoma coerulescens (Bednekoff & Woolfenden, 2003, 2006, pied babblers, Turdoides bicolor (Hollen et al, 2011), white-browed sparrow weaver, Plocepasser mahali (Walker, York, & Young, 2016) and meerkats, Suricata suricatta (Clutton-Brock et al, 1999), dominants act as sentinels significantly more than subordinates. In dwarf mongoose, Helogale undulata, Rasa (1986) found that subordinates sentinel more than dominants, but these findings were overturned in Kern, Sumner, and Radford (2016).…”

Section: Introductionmentioning

confidence: 99%

“…In the Arabian babbler, Turdoides squamiceps (Wright, Berg, Kort, Khazin, & Maklakov, 2001a;Wright et al, 2001b), Florida scrub-jay, Aphelocoma coerulescens (Bednekoff & Woolfenden, 2003, 2006, pied babblers, Turdoides bicolor (Hollen et al, 2011), white-browed sparrow weaver, Plocepasser mahali (Walker, York, & Young, 2016) and meerkats, Suricata suricatta (Clutton-Brock et al, 1999), dominants act as sentinels significantly more than subordinates. In the Arabian babbler, Turdoides squamiceps (Wright, Berg, Kort, Khazin, & Maklakov, 2001a;Wright et al, 2001b), Florida scrub-jay, Aphelocoma coerulescens (Bednekoff & Woolfenden, 2003, 2006, pied babblers, Turdoides bicolor (Hollen et al, 2011), white-browed sparrow weaver, Plocepasser mahali (Walker, York, & Young, 2016) and meerkats, Suricata suricatta (Clutton-Brock et al, 1999), dominants act as sentinels significantly more than subordinates.…”

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confidence: 99%

The sentineling—Foraging trade‐off in dominant and subordinate Arabian babblers

Ostreiher

Heifetz

2019

Ethology

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Many cooperative breeders forage under predation risks, sentineling is a central activity, and groupmates have to balance between sentineling and foraging. The optimal balance between sentinel activity and foraging may differ among dominant and subordinate individuals, as dominants are more efficient foragers. Two theoretical models pertain to this balance and predict when individuals with different foraging abilities should switch between the two activities on the basis of their energetic state. In one of these models, individuals must attain a critical energetic level by dusk to pass the night, and in the second model fitness is monotonically increasing with the energetic state. We tested these models in the cooperatively breeding Arabian babbler, Turdoides squamiceps. We measured the length of sentinel bouts and the gaps between them both in natural conditions and following experimental feeding. Following feeding ad libitum, subordinates expanded their sentinel bouts significantly more than dominants in comparison with natural conditions. These findings are consistent with the first model, but not with the second. In the experiment, we measured the mass of mealworms consumed by each individual following a sentinel bout relative to its body mass. This ratio was larger for subordinates, indicating that they ended their sentinel bouts at a lower energetic state than dominants. This finding is consistent with the second model, but not with the first. Immediately after eating ad libitum, in 62% of the cases the first behavior performed by the babblers was a new sentinel bout, but in 17% it was a mutual interaction with a groupmate, indicating that social interactions also play a role in the trade‐off vis‐à‐vis sentinel activity.

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Sexually selected sentinels? Evidence of a role for intrasexual competition in sentinel behavior

Cited by 24 publications

References 49 publications

Telomere attrition predicts reduced survival in a wild social bird, but short telomeres do not

Telomere attrition predicts reduced survival in a wild social bird, but short telomeres do not

The sentinel behaviour of Arabian babbler floaters

The sentineling—Foraging trade‐off in dominant and subordinate Arabian babblers

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