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2.  How the bat got its buzz 
Biology Letters  2013;9(2):20121031.
Since the discovery of echolocation in bats, the final phase of an attack on a flying insect, the ‘terminal buzz’, has proved enigmatic. During the buzz, bats increase information update rates by producing vocalizations up to 220 times s−1. The buzz's ubiquity in hawking and trawling bats implies its importance for hunting success. Superfast muscles, previously unknown in mammals, are responsible for the extreme vocalization rate. Some bats produce a second phase—buzz II—defined by a large drop in the fundamental frequency (F0) of their calls. By doing so, bats broaden their acoustic field of view and should thereby reduce the likelihood of insect escape. We make the case that the buzz was a critical adaptation for capturing night-flying insects, and suggest that the drop in F0 during buzz II requires novel, unidentified laryngeal mechanisms in order to counteract increasing muscle tension. Furthermore, we propose that buzz II represents a countermeasure against the evasive flight of eared prey in the evolutionary arms-race that saw the independent evolution of bat-detecting ears in various groups of night-flying insects.
doi:10.1098/rsbl.2012.1031
PMCID: PMC3639754  PMID: 23302868
bats; echolocation; terminal buzz; superfast muscles; acoustic field of view
4.  Leaf morphology shift is not linked to climate change 
Biology Letters  2013;9(1):20120659.
doi:10.1098/rsbl.2012.0659
PMCID: PMC3565485  PMID: 23118433
5.  Chronometry for the chorusing herd: Hamilton's legacy on context-dependent acoustic signalling—a comment on Herbers (2013) 
Biology Letters  2014;10(1):20131018.
doi:10.1098/rsbl.2013.1018
PMCID: PMC3917344  PMID: 24429686
synchronization; chorusing; rhythm; selfish herd; origins of music; agent-based model
7.  Pro-sociality without empathy 
Biology Letters  2012;8(6):910-912.
Empathy, the capacity to recognize and share feelings experienced by another individual, is an important trait in humans, but is not the same as pro-sociality, the tendency to behave so as to benefit another individual. Given the importance of understanding empathy's evolutionary emergence, it is unsurprising that many studies attempt to find evidence for it in other species. To address the question of what should constitute evidence for empathy, we offer a critical comparison of two recent studies of rescuing behaviour that report similar phenomena but are interpreted very differently by their authors. In one of the studies, rescue behaviour in rats was interpreted as providing evidence for empathy, whereas in the other, rescue behaviour in ants was interpreted without reference to sharing of emotions. Evidence for empathy requires showing that actor individuals possess a representation of the receiver's emotional state and are driven by the psychological goal of improving its wellbeing. Proving psychological goal-directedness by current standards involves goal-devaluation and causal sensitivity protocols, which, in our view, have not been implemented in available publications. Empathy has profound significance not only for cognitive and behavioural sciences but also for philosophy and ethics and, in our view, remains unproven outside humans.
doi:10.1098/rsbl.2012.0554
PMCID: PMC3497120  PMID: 22859561
empathy; pro-social behaviour; intentionality; goal-directedness
8.  The ontogenetic origins of mirror neurons: evidence from ‘tool-use’ and ‘audiovisual’ mirror neurons 
Biology Letters  2012;8(5):856-859.
Since their discovery, mirror neurons—units in the macaque brain that discharge both during action observation and execution—have attracted considerable interest. Whether mirror neurons are an innate endowment or acquire their sensorimotor matching properties ontogenetically has been the subject of intense debate. It is widely believed that these units are an innate trait; that we are born with a set of mature mirror neurons because their matching properties conveyed upon our ancestors an evolutionary advantage. However, an alternative view is that mirror neurons acquire their matching properties during ontogeny, through correlated experience of observing and performing actions. The present article re-examines frequently overlooked neurophysiological reports of ‘tool-use’ and ‘audiovisual’ mirror neurons within the context of this debate. It is argued that these findings represent compelling evidence that mirror neurons are a product of sensorimotor experience, and not an innate endowment.
doi:10.1098/rsbl.2012.0192
PMCID: PMC3440963  PMID: 22573832
mirror neurons; associative learning; audiovisual mirror neurons; tool-use mirror neurons
9.  Is more better? Polyploidy and parasite resistance 
Biology Letters  2012;8(4):598-600.
Ploidy-level variation is common and can drastically affect organismal fitness. We focus on the potential consequences of this variation for parasite resistance. First, we elucidate connections between ploidy variation and key factors determining resistance, including allelic diversity, gene expression and physiological condition. We then argue that systems featuring both natural and artificially manipulated ploidy variation should be used to evaluate whether ploidy level influences host–parasite interactions.
doi:10.1098/rsbl.2011.1152
PMCID: PMC3391438  PMID: 22258448
polyploidy; host–parasite interactions; allelic diversity; gene expression; host condition
10.  Plasticity of preferred body temperatures as means of coping with climate change? 
Biology Letters  2011;8(2):262-265.
Thermoregulatory behaviour represents an important component of ectotherm non-genetic adaptive capacity that mitigates the impact of ongoing climate change. The buffering role of behavioural thermoregulation has been attributed solely to the ability to maintain near optimal body temperature for sufficiently extended periods under altered thermal conditions. The widespread occurrence of plastic modification of target temperatures that an ectotherm aims to achieve (preferred body temperatures) has been largely overlooked. I argue that plasticity of target temperatures may significantly contribute to an ectotherm's adaptive capacity. Its contribution to population persistence depends on both the effectiveness of acute thermoregulatory adjustments (reactivity) in buffering selection pressures in a changing thermal environment, and the total costs of thermoregulation (i.e. reactivity and plasticity) in a given environment. The direction and magnitude of plastic shifts in preferred body temperatures can be incorporated into mechanistic models, to improve predictions of the impact of global climate change on ectotherm populations.
doi:10.1098/rsbl.2011.0960
PMCID: PMC3297409  PMID: 22072284
acclimation; climate change; ectotherms; thermoregulatory behaviour
11.  On the inference of function from structure using biomechanical modelling and simulation of extinct organisms 
Biology Letters  2011;8(1):115-118.
Biomechanical modelling and simulation techniques offer some hope for unravelling the complex inter-relationships of structure and function perhaps even for extinct organisms, but have their limitations owing to this complexity and the many unknown parameters for fossil taxa. Validation and sensitivity analysis are two indispensable approaches for quantifying the accuracy and reliability of such models or simulations. But there are other subtleties in biomechanical modelling that include investigator judgements about the level of simplicity versus complexity in model design or how uncertainty and subjectivity are dealt with. Furthermore, investigator attitudes toward models encompass a broad spectrum between extreme credulity and nihilism, influencing how modelling is conducted and perceived. Fundamentally, more data and more testing of methodology are required for the field to mature and build confidence in its inferences.
doi:10.1098/rsbl.2011.0399
PMCID: PMC3259946  PMID: 21666064
musculoskeletal system; dinosaur; computer modelling; simulation; palaeontology; biomechanics
12.  Models in palaeontological functional analysis 
Biology Letters  2011;8(1):119-122.
Models are a principal tool of modern science. By definition, and in practice, models are not literal representations of reality but provide simplifications or substitutes of the events, scenarios or behaviours that are being studied or predicted. All models make assumptions, and palaeontological models in particular require additional assumptions to study unobservable events in deep time. In the case of functional analysis, the degree of missing data associated with reconstructing musculoskeletal anatomy and neuronal control in extinct organisms has, in the eyes of some scientists, rendered detailed functional analysis of fossils intractable. Such a prognosis may indeed be realized if palaeontologists attempt to recreate elaborate biomechanical models based on missing data and loosely justified assumptions. Yet multiple enabling methodologies and techniques now exist: tools for bracketing boundaries of reality; more rigorous consideration of soft tissues and missing data and methods drawing on physical principles that all organisms must adhere to. As with many aspects of science, the utility of such biomechanical models depends on the questions they seek to address, and the accuracy and validity of the models themselves.
doi:10.1098/rsbl.2011.0674
PMCID: PMC3259975  PMID: 21865242
palaeobiology; biomechanics; function; feeding; locomotion
13.  On the flexibility of lizards' cognition: a comment on Leal & Powell (2011) 
Biology Letters  2011;8(1):42-43.
doi:10.1098/rsbl.2011.0848
PMCID: PMC3259984  PMID: 22158735
15.  Epidemiological consequences of a newly discovered cryptic subgroup of Anopheles gambiae 
Biology Letters  2011;7(6):947-949.
A cryptic subgroup of Anopheles gambiae sensu stricto mosquitoes was recently discovered in West Africa. This ‘GOUNDRY’ subgroup has increased susceptibility to Plasmodium falciparum, the most deadly form of malaria. Unusual for this major malaria vector, GOUNDRY mosquitoes also seem to bite exclusively outdoors. A mathematical model is developed to assess the epidemiological implications of current vector control tools, bednets and indoor residual spray, preferentially suppressing the more typical indoor biting mosquitoes. It is demonstrated that even if the GOUNDRY mosquitoes have a decreased preference for human blood, vector controls which select for increased GOUNDRY abundance relative to their indoor biting counterparts risks intensifying malaria transmission. Given the widely observed phenomenon of outdoor biting by major malaria vectors, this behaviour should not be ignored in future modelling efforts and warrants serious consideration in control programme strategy.
doi:10.1098/rsbl.2011.0453
PMCID: PMC3210673  PMID: 21693489
malaria; vectorial capacity; Lotka–Volterra model
16.  Of global space or perceived place? Comment on Kelly et al. 
Biology Letters  2011;7(5):647-648.
doi:10.1098/rsbl.2011.0216
PMCID: PMC3169059  PMID: 21673051
17.  Taxonomic counts of cognition in the wild 
Biology Letters  2010;7(4):631-633.
In 1985, Kummer & Goodall pleaded for an ecology of intelligence and proposed that innovations might be a good way to measure cognition in the wild. Counts of innovation per taxonomic group are now available in hundreds of avian and primate species, as are counts of tactical deception, tool use and social learning. Robust evidence suggests that innovation rate and its neural correlates allow birds and mammals to cope better with environmental change. The positive correlations between taxonomic counts, and the increasing number of cognitive and neural measures found to be associated with ecological variables, suggest that domain general processes might be more pervasive than previously thought in the evolution of intelligence.
doi:10.1098/rsbl.2010.0556
PMCID: PMC3130206  PMID: 20719769
innovation rate; tool use; social learning; tactical deception; brain size; general intelligence
18.  Nemo through the looking-glass: a commentary on Desjardins & Fernald 
Biology Letters  2011;7(4):487-488.
doi:10.1098/rsbl.2010.0760
PMCID: PMC3130208  PMID: 21525054
19.  Oribatid mites and skin alkaloids in poison frogs 
Biology Letters  2011;7(4):555-556.
doi:10.1098/rsbl.2010.1113
PMCID: PMC3130211  PMID: 21345855
20.  Peptide transport and animal growth: the fish paradigm 
Biology Letters  2011;7(4):597-600.
Protein digestion products are transported from the intestinal lumen into the enterocyte both in the form of free amino acids (AAs), by a large variety of brush border membrane AA transporters, and in the form of di/tripeptides, by a single brush border membrane transporter known as PEPtide Transporter 1 (PEPT1). Recent data indicate that, at least in teleost fish, PEPT1 plays a significant role in animal growth by operating, at the gastrointestinal level, as part of an integrated response network to food availability that directly supports body weight. Notably, PEPT1 responds to both fasting and refeeding and is involved in a phenomenon known as compensatory growth (a phase of accelerated growth when food levels are restored after a period of growth depression). In particular, PEPT1 expression decreases during fasting and increases during refeeding, which is the opposite of what observed so far in mammals and birds. These findings in teleost fish document, to our knowledge, for the first time in a vertebrate model, a direct correlation between the expression of an intestinal transporter, such as PEPT1, primarily involved in the uptake of dietary protein degradation products and animal growth.
doi:10.1098/rsbl.2010.1164
PMCID: PMC3130217  PMID: 21389019
di/tripeptides; PEPtide Transporter 1; teleost fish; growth; fasting/refeeding
21.  ‘Canis empathicus’? A proposal on dogs' capacity to empathize with humans 
Biology Letters  2011;7(4):489-492.
Empathy has long attracted the attention of philosophers and psychologists, and more recently, of evolutionary biologists. Interestingly, studies suggest that empathy is a phylogenetically continuous phenomenon, ranging across animals from automatic emotional activation in response to the emotions of others, to perspective-taking that becomes increasingly complex with increasing brain size. Although suggestions have been made that the domestic dog may have the capacity to empathize with humans, no discussion has yet addressed the topic, nor have experimental routes been proposed to further explore the level of emotional and cognitive processing underlying dogs' seemingly empathic behaviour towards humans. In this opinion piece, we begin by contextualizing our topic of interest within the larger body of literature on empathy. Thereafter we: (i) outline the reasons for why we believe dogs may be capable of empathizing with humans, perhaps even at some level beyond emotional contagion; (ii) review available evidence both pro and against our opinion; and (iii) propose routes for future studies to accurately address the topic. Also, we consider the use of dogs to further explore open questions regarding empathy in humans.
doi:10.1098/rsbl.2011.0083
PMCID: PMC3130240  PMID: 21325312
behaviour; domestic dog; cognition; empathy; emotions
22.  Biologically meaningful coverage indicators for eliminating malaria transmission 
Biology Letters  2012;8(5):874-877.
Mosquitoes, which evade contact with long-lasting insecticidal nets and indoor residual sprays, by feeding outdoors or upon animals, are primary malaria vectors in many tropical countries. They can also dominate residual transmission where high coverage of these front-line vector control measures is achieved. Complementary strategies, which extend insecticide coverage beyond houses and humans, are required to eliminate malaria transmission in most settings. The overwhelming diversity of the world's malaria transmission systems and optimal strategies for controlling them can be simply conceptualized and mapped across two-dimensional scenario space defined by the proportion of blood meals that vectors obtain from humans and the proportion of human exposure to them which occurs indoors.
doi:10.1098/rsbl.2012.0352
PMCID: PMC3440981  PMID: 22647930
GFK insecticides; coverage; malaria; animal; outdoor; mosquito
23.  Blackawton bees: commentary on Blackawton, P. S. et al. 
Biology Letters  2010;7(2):166-167.
doi:10.1098/rsbl.2010.1057
PMCID: PMC3061191  PMID: 21177691
24.  The May threshold and life-history allometry 
Biology Letters  2010;6(6):850-853.
One of Robert May's classic results was finding that population dynamics become chaotic when the average lifetime rate of reproduction exceeds a certain value. Populations whose reproductive rates exceed this May threshold probably become extinct. The May threshold in each case depends upon the shape of the density-dependence curve, which differs among models of population growth. However, species of different sizes and generation times that share a roughly similar density-dependence curve will also share a similar May threshold. Here, we argue that this fact predicts a striking allometric regularity among animal taxa: lifetime reproductive rate should be roughly independent of body size. Such independence has been observed in diverse taxa, but has usually been ascribed to a fortuitous combination of physiologically based life-history allometries. We suggest, instead, that the ecological elimination of unstable populations within groups that share a value of the May threshold is a likely cause of this allometry.
doi:10.1098/rsbl.2010.0452
PMCID: PMC3001382  PMID: 20591855
population growth rate; lifetime reproduction; chaos; body size; population extinction; ecological elimination

Results 1-25 (94)