29 research outputs found
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
Biopolymer dynamics driven by helical flagella
Microbial flagellates typically inhabit complex suspensions of polymeric
material which can impact the swimming speed of motile microbes, filter-feeding
of sessile cells, and the generation of biofilms. There is currently a need to
better understand how the fundamental dynamics of polymers near active cells or
flagella impacts these various phenomena, in particular the hydrodynamic and
steric influence of a rotating helical filament on suspended polymers. Our
Stokesian dynamics simulations show that as a stationary rotating helix pumps
fluid along its long axis, polymers migrate radially inwards while being
elongated. We observe that the actuation of the helix tends to increase the
probability of finding polymeric material within its pervaded volume. This
accumulation of polymers within the vicinity of the helix is stronger for
longer polymers. We further analyse the stochastic work performed by the helix
on the polymers and show that this quantity is positive on average and
increases with polymer contour length.Comment: 14 pages, 6 figure
Evidence for contrasting roles for prolactin in eusocial naked mole-rats, Heterocephalus glaber and Damaraland mole-rats, Fukomys damarensis
Elevated prolactin (PRL) has been associated with the expression of social and cooperative behaviours in a number of vertebrate species, as well as suppression of reproduction. As social mole-rats exhibit both of these traits, PRL is a prime candidate in mediating their social phenotype. While naked and Damaraland mole-rats (NMRs and DMRs) have evolved eusociality independently within their family, both species exhibit an extreme skew in lifetime reproductive success, with breeding restricted to a single female and one or two males. Non-breeding NMRs of both sexes are physiologically inhibited from reproducing, while in DMRs only the non-breeding females are physiologically suppressed. Newly emerging work has implicated the dopamine system and PRL as a component in socially induced reproductive suppression and eusociality in NMR, but the DMR remains unstudied in this context. To investigate evolutionary convergence in the role of PRL in shaping African mole-rat eusociality, we determined plasma PRL concentrations in breeders and non-breeders of both sexes, comparing DMRs with NMRs. Among samples from non-breeding NMRs 80% had detectable plasma PRL concentrations. As a benchmark, these often (37%) exceeding those considered clinically hyperprolactinaemic (25 ng mlâ1) in humans: mean ± s.e.m.: 34.81 ± 5.87 ngmlâ1; range 0.00â330.30 ng mlâ1. Conversely, 85% of non-breeding DMR samples had undetectable values and none had concentrations above 25 ng mlâ1: 0.71 ± 0.38 ng mlâ1; 0.00â23.87 ngmlâ1. Breeders in both species had the expected variance in plasma PRL concentrations as part of normal reproductive function, with lactating queens having significantly higher values. These results suggest that while elevated PRL in non-breeders is implicated in NMR eusociality, this may not be the case in DMRs, and suggests a lack of evolutionary convergence in the proximate control of the social phenotype in these mole-rats.SARCHI Chair to NCB (Grant N64756)http://rsbl.royalsocietypublishing2019-05-01hj2018Anatomy and PhysiologyMammal Research InstituteZoology and Entomolog
Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay
In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the 'pay-to-stay' hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced 'idle' period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously, idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers
Body weight prediction using body size measurements in Fleckvieh, Holstein, and Brown Swiss dairy cows in lactation and dry periods
The objective of this study was to predict cows'
body weight from body size measurements and other animal data in the
lactation and dry periods. During the whole year 2014, 6306 cows (on
167Â commercial Austrian dairy farms) were weighed at each routine performance
recording and body size measurements like heart girth (HG), belly girth (BG),
and body condition score (BCS) were recorded. Data on linear traits like hip
width (HW), stature, and body depth were collected three times a year. Cows
belonged to the genotypes Fleckvieh (and Red Holstein crosses), Holstein, and
Brown Swiss. Body measurements were tested as single predictors and in
multiple regressions according to their prediction accuracy and their
correlations with body weight. For validation, data sets were split randomly
into independent subsets for estimation and validation. Within the prediction
models with a single body measurement, heart girth influenced relationship
with body weight most, with a lowest root mean square error (RMSE) of
39.0 kg, followed by belly girth (39.3 kg) and hip width (49.9 kg). All
other body measurements and BCS resulted in a RMSE of higher than 50.0Â kg.
The model with heart and belly girth (ModelHGâ
BG) reduced RMSE to
32.5 kg, and adding HW reduced it further to
30.4 kg (ModelHGâ
BGâ
HW). As RMSE and the coefficient of
determination improved, genotype-specific regression coefficients for body
measurements were introduced in addition to the pooled ones. The most
accurate equations, ModelHGâ
BG and ModelHGâ
BGâ
HW,
were validated separately for the lactation and dry periods. Root mean square
prediction error (RMSPE) ranged between 36.5 and 37.0 kg
(ModelHGâ
BGâ
HW, ModelHGâ
BG, lactation) and 39.9Â and
41.3 kg (ModelHGâ
BGâ
HW, ModelHGâ
BG, dry period).
Accuracy of the predictions was evaluated by decomposing the mean square
prediction error (MSPE) into error due to central tendency, error due to
regression, and error due to disturbance. On average, 99.6 % of the
variance between estimated and observed values was caused by disturbance,
meaning that predictions were valid and without systematic estimation error.
On the one hand, this indicates that the chosen traits sufficiently depicted
factors influencing body weight. On the other hand, the data set was very
heterogeneous and large. To ensure high prediction accuracy, it was necessary
to include body girth traits for body weight estimation.</p
âQuae voces audio?â Some
questions regarding the exploration of medieval British childhood
Benefits of cooperation in captive Damaraland mole-rats
Although the social mole-rats are commonly classified as eusocial breeders on the grounds that groups include a single breeding female (the âqueenâ) and a number of nonbreeding individuals (âhelpersâ) of both sexes, alloparental care is not highly developed in these species and there is no direct evidence that the presence or number of nonbreeders is associated with reductions in the workload of the âqueen.â An alternative interpretation of mole-rat groups is that the social mole-rats are cooperative foragers rather than cooperative or eusocial breeders. Here, in captive colonies of Damaraland mole-rats (Fukomys damarensis), we provide the first evidence that increases in the number of nonbreeding subordinates in mole-rat groups are associated with reductions in the workload of âqueensâ and with increases in their fecundity.The European Research Council and the Human Frontier Science Program.https://academic.oup.com/beheco2021-03-12hj2020Mammal Research InstituteZoology and Entomolog
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Damaraland mole-rats do not rely on helpers for reproduction or survival
Abstract
In eusocial invertebrates and obligate cooperative breeders, successful reproduction is dependent on assistance from non-breeding group members. Although naked (Heterocephalus glaber) and Damaraland mole-rats (Fukomys damarensis) are often described as eusocial and their groups are suggested to resemble those of eusocial insects more closely than groups of any other vertebrate, the extent to which breeding individuals benefit from the assistance of non-breeding group members is unclear. Here we show that, in wild Damaraland mole-rats, prospective female breeders usually disperse and settle alone in new burrow systems where they show high survival rates and remain in good body conditionâoften for several yearsâbefore being joined by males. In contrast to many obligate cooperative vertebrates, pairs reproduced successfully without non-breeding helpers, and the breeding success of experimentally formed pairs was similar to that of larger, established groups. Though larger breeding groups recruited slightly more pups than smaller groups, adult survival was independent of group size and group size had mixed effects on the growth of non-breeders. Our results suggest that Damaraland mole-rats do not need groups to survive and that cooperative breeding in the species is not obligate as pairs canâand frequently doâreproduce without the assistance of helpers. While re-emphasizing the importance of ecological constraints on dispersal in social mole-rats, the mixed effects of group size in our study suggest that indirect benefits accrued through cooperative behavior may have played a less prominent role in the evolution of mole-rat group-living than previously thought.</jats:p