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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.03.011 Byline: Joah R. Madden (a), Hans-Joerg P. Kunc (b), Sinead English (a), Tim H. Clutton-Brock (a) Abstract: Begging by young provokes adults to provide food for them. However, eventually begging by young and provisioning by adults cease and young become nutritionally independent. Why do young cease begging and so forgo food brought to them by adults? Three explanations have been proposed: (1) adults may not respond to begging anymore and cease feeding begging young; (2) young may voluntarily switch from begging to independent foraging as they gain more rewards from this; (3) young may become unable to produce stimulating begging calls. We tested these three explanations using meerkat, Suricata suricatta, pups. Playback of begging calls at groups where begging had naturally ceased provoked adults to resume provisioning, suggesting that adults had not stopped responding to begging. Experimental provision of food to pups mimicking either natural pup feeding or foraging success produced no differences in subsequent changes in begging or foraging behaviour, suggesting that pups were not assessing the most rewarding means of obtaining food and switching from begging to foraging accordingly. The begging calls of pups (aged 40-60 days) were acoustically different to those produced when they were juveniles (aged 100-120 days), and adults discriminated between rate-controlled playbacks of the two age classes of calls, delivering less food to calls of a juvenile than to the same individual's calls recorded when a pup. Adult meerkats paid attention to the acoustic structure of begging calls, and ceased provisioning when the call structure changed. We suggest that older pups are unable to produce stimulating begging calls. Author Affiliation: (a) Large Animal Research Group, Department of Zoology, University of Cambridge, U.K. (b) Verhaltensbiologie, Zoologisches Institut, Universitat Zurich-Irchel, Switzerland Article History: Received 4 December 2008; Revised 19 January 2009; Accepted 27 March 2009 Article Note: (miscellaneous) MS. number: 08-00775R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2008.07.027 Byline: Marta B. Manser, Joah R. Madden, Hansjoerg P. Kunc, Sinead English, Tim Clutton-Brock Abstract: In many bird species with biparental care for young in the nest, hungry chicks beg repeatedly and parents adjust their feeding rate to the call rate of young. Repetitive calling also occurs in fledglings and in some mammals where offspring follow provisioners. It is not yet clear whether, in mobile systems with dispersed young where adults cannot compare the vocal behaviour of all young simultaneously, the calls represent a signal of need. We investigated repetitive begging by cooperatively reared meerkat, Suricata suricatta, pups that foraged with the group. Pups produced two types of begging calls: repeat calls over long periods and high-pitched calls mainly confined to feeding events. Food-deprived pups stayed closer to feeders, and begged for longer and more intensely by calling at a higher rate. Hungry pups increased both the rate of repeat calls, which were given continually, and the number of high-pitched bouts, but adults increased their food allocation only in relation to the rate of repeat calls. Our study indicates that hunger may lead to several changes in vocal behaviour, only some of which may be used by adults to assess need. Author Affiliation: (a) Verhaltensbiologie, Zoologisches Institut, Universitat Zurich, Switzerland (a ) Mammal Research Institute, University of Pretoria, South Africa (a ) Department of Zoology, University of Cambridge, U.K. Article History: Received 8 January 2008; Revised 14 March 2008; Accepted 29 July 2008 Article Note: (miscellaneous) MS. number: 08-00015R

All organisms have a stress response system to cope with environmental threats, yet its precise form varies hugely within and across individuals, populations, and species. While the physiological mechanisms are increasingly understood, how stress responses have evolved remains elusive. Here, we show that important insights can be gained from models that incorporate physiological mechanisms within an evolutionary optimality analysis (the 'evo-mecho' approach). Our approach reveals environmental predictability and physiological constraints as key factors shaping stress response evolution, generating testable predictions about variation across species and contexts. We call for an integrated research programme combining theory, experimental evolution, and comparative analysis to advance scientific understanding of how this core physiological system has evolved. Extensive experimental and comparative studies provide a solid understanding of the physiological basis of the stress response system and its variation across and within species. However, lagging behind this is a formal theoretical framework to help unify the wealth of existing verbal hypotheses linking stress response mechanisms and fitness, and to explain how such a response system has evolved. We propose an evo-mecho approach, combining optimality models and evolutionary simulations with empirical evidence about the underlying physiology, to show how mechanistic constraints and the predictability of environmental risks shape the stress response. A deeper understanding of stress response evolution will require mechanistically informed evolutionary models, phylogenetically controlled comparative analyses, and experimental evolution studies. [ABSTRACT FROM AUTHOR]

Critical thermal maximum (CT max) describes the upper thermal tolerance of an animal where biological functions start to fail. A period of acclimation can enhance CT max through plasticity, potentially buffering animals from extreme temperatures caused by climate change. Basal and acclimated CT max vary within and between species and may be explained by traits related to thermal physiology, such as body size and sex. Differences in CT max have not been established among species of tsetse fly (Glossina spp.), vectors of animal and human African trypanosomiasis. Here, we investigated basal CT max and its plasticity for five tsetse species following adult acclimation at constant 25 or 30 °C for five days. We then set our findings in context using a meta-analysis on 33 species of Diptera. We find that, of the five tsetse species considered, only Glossina palpalis gambiensis and Glossina brevipalpis exhibited plasticity of CT max , with an increase of 0.12 °C and 0.10 °C per 1 °C acclimation respectively. Within some species, higher basal CT max values were associated with larger body size and being female, while variation in plasticity (i.e., response to the acclimation temperature) could not be explained by sex or size. Our broader meta-analysis across Diptera revealed overall CT max plasticity of 0.06 °C per 1 °C acclimation, versus a similar 0.05 °C mean increase in tsetse. In contrast, there was greater CT max plasticity in males compared to females in Diptera. Our study highlights that CT max and its plasticity varies even among closely related species. Broader patterns across groups are not always reflected at a finer resolution; we thus emphasise the need for detailed experimental studies across a wide range of insect species to capture their capacity to cope with rapidly warming temperatures. • Thermal tolerance can inform how disease vectors will respond to climate change. • We compare the plasticity of critical thermal maximums (CT max) among five tsetse species. • Acclimation increased CT max in two of five species. • Larger body size and being female was related to higher basal CT max values. • Weak plasticity and small body size is likely to hinder tsetse in a warming world. [ABSTRACT FROM AUTHOR]

South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating invasive global insect pest of tomato, Solanum lycopersicum (Solanaceae). In nature, pests face multiple overlapping environmental stressors, which may significantly influence survival. To cope with rapidly changing environments, insects often employ a suite of mechanisms at both acute and chronic time-scales, thereby improving fitness at sub-optimal thermal environments. For T. absoluta , physiological responses to transient thermal variability remain under explored. Moreso, environmental effects and physiological responses may differ across insect life stages and this can have implications for population dynamics. Against this background, we investigated short and long term plastic responses to temperature of T. absoluta larvae (4th instar) and adults (24–48 h old) from field populations. We measured traits of temperature tolerance vis critical thermal limits [critical thermal minima (CT min) and maxima (CT max)], heat knockdown time (HKDT), chill coma recovery time (CCRT) and supercooling points (SCP). Our results showed that at the larval stage, Rapid Cold Hardening (RCH) significantly improved CT min and HKDT but impaired SCP and CCRT. Heat hardening in larvae impaired CT min , CCRT, SCP, CT max but not HKDT. In adults, both heat and cold hardening generally impaired CT min and CT max , but had no effects on HKDT, SCP and CCRT. Low temperature acclimation significantly improved CT min and HKDT while marginally compromising CCRT and CT max , whereas high temperature acclimation had no significant effects on any traits except for HKDT in larvae. Similarly, low and high temperature acclimation had no effects on CT min , SCPs and CT max , while high temperature acclimation significantly compromised adult CCRT. Our results show that larvae are more thermally plastic than adults and can shift their thermal tolerance in short and long timescales. The larval plasticity reported here could be advantageous in new envirnments, suggesting an asymmetrical ecological role of larva relative to adults in facilitating T. absoluta invasion. • Short- and long-term acclimation induced thermal plasticity in T. absoluta with larvae being more plastic than adults. • Rapid cold hardening improved larval low (CT min) and high (HKDT) temperature tolerance. • Low temperature acclimation improved cold (CT min) and heat (HKDT) tolerance in larvae. • Short- and -long term acclimation impaired CT max, SCP and CCRT respectively in adults. [ABSTRACT FROM AUTHOR]