Two modes of input processing in relation to risk of sperm competition in mammals

Much research has been focused on the ‘output’ or response of males to particular risks of sperm competition (RSC). Lately, there has also been some interest on the types of information that males may use to assess RSC (RSC inputs). In contrast, there is a lack of studies on how males may process RSC inputs to generate such RSC outputs. Here we propose two modes of input processing (direct and indirect) and ways to test them in order to understand how a male may process and store RSC information. The direct mode of input processing predicts that a male may store RSC inputs through a physiological response, e.g., through a change in hormonal levels. As long as this response is active, the male will stay in a ‘RSC state’ and will produce an RSC output (e.g. high sperm investment) instead of a non-RSC output (e.g. relatively lower sperm investment) when he encounters a female. The indirect mode of input processing predicts that a male may store RSC inputs in his memory and retrieve such information later on to modify his output (e.g. sperm investment or copulatory behavior) accordingly. We use a multidisciplinary approach that should appeal to those researchers that seek to understand male’s adaptations to sperm competition at different levels. We believe that the testing of the hypotheses developed in this paper will lead to interesting findings and the development of new hypothese

A Comparison of Scent Marking between a Monogamous and Promiscuous Species of Peromyscus: Pair Bonded Males Do Not Advertise to Novel Females

Scent marking can provide behavioral and physiological information including territory ownership and mate advertisement. It is unknown how mating status and pair cohabitation influence marking by males from different social systems. We compared the highly territorial and monogamous California mouse (Peromyscus californicus) to the less territorial and promiscuous white-footed mouse (P. leucopus). Single and mated males of both species were assigned to one of the following arenas lined with filter paper: control (unscented arena), male scented (previously scent-marked by a male conspecific), or females present (containing females in small cages). As expected, the territorial P. californicus scent marked and overmarked an unfamiliar male conspecific's scent marks more frequently than P. leucopus. Species differences in responses to novel females were also found based on mating status. The presence of unfamiliar females failed to induce changes in scent marking in pair bonded P. californicus even though virgin males increased marking behavior. Pair bonding appears to reduce male advertisement for novel females. This is in contrast to P. leucopus males that continue to advertise regardless of mating status. Our data suggest that communication through scent-marking can diverge significantly between species based on mating system and that there are physiological mechanisms that can inhibit responsiveness of males to female cues

Olfactory Sex Recognition Investigated in Antarctic Prions

Chemical signals can yield information about an animal such as its identity, social status or sex. Such signals have rarely been considered in birds, but recent results have shown that chemical signals are actually used by different bird species to find food and to recognize their home and nest. This is particularly true in petrels whose olfactory anatomy is among the most developed in birds. Recently, we have demonstrated that Antarctic prions, Pachyptila desolata, are also able to recognize and follow the odour of their partner in a Y-maze

Genetically-Based Olfactory Signatures Persist Despite Dietary Variation

Individual mice have a unique odor, or odortype, that facilitates individual recognition. Odortypes, like other phenotypes, can be influenced by genetic and environmental variation. The genetic influence derives in part from genes of the major histocompatibility complex (MHC). A major environmental influence is diet, which could obscure the genetic contribution to odortype. Because odortype stability is a prerequisite for individual recognition under normal behavioral conditions, we investigated whether MHC-determined urinary odortypes of inbred mice can be identified in the face of large diet-induced variation. Mice trained to discriminate urines from panels of mice that differed both in diet and MHC type found the diet odor more salient in generalization trials. Nevertheless, when mice were trained to discriminate mice with only MHC differences (but on the same diet), they recognized the MHC difference when tested with urines from mice on a different diet. This indicates that MHC odor profiles remain despite large dietary variation. Chemical analyses of urinary volatile organic compounds (VOCs) extracted by solid phase microextraction (SPME) and analyzed by gas chromatography/mass spectrometry (GC/MS) are consistent with this inference. Although diet influenced VOC variation more than MHC, with algorithmic training (supervised classification) MHC types could be accurately discriminated across different diets. Thus, although there are clear diet effects on urinary volatile profiles, they do not obscure MHC effects

Chimpanzees (Pan troglodytes) Fail a What-Where-When Task but Find Rewards by Using a Location-Based Association Strategy

Recollecting the what-where-when of an episode, or episodic-like memory, has been established in corvids and rodents. In humans, a linkage between remembering the past and imagining the future has been recognised. While chimpanzees can plan for the future, their episodic-like memory has hardly been investigated. We tested chimpanzees (Pan troglodytes) with an adapted food-caching paradigm. They observed the baiting of two locations amongst four and chose one after a given delay (15 min, 1 h or 5 h). We used two combinations of food types, a preferred and a less preferred food that disappeared at different rates. The subjects had to base their choices on the time elapsed since baiting, and on their memory of which food was where. They could recover either their preferred food or the one that remained present. All animals failed to obtain the preferred or present foods above chance levels. They were like-wise unsuccessful at choosing baited cups above chance levels. The subjects, thus, failed to use any feature of the baiting events to guide their choices. Nonetheless, their choices were not random, but the result of a developed location-based association strategy. Choices in the second half of the study correlated with the rewards obtained at each location in the first half of the study, independent from the choices made for each location in the first half of the study. This simple location-based strategy yielded a fair amount of food. The animals' failure to remember the what-where-when in the presented set-up may be due to the complexity of the task, rather than an inability to form episodic-like memories, as they even failed to remember what was where after 15 minutes

Neural Circuits Underlying Rodent Sociality: A Comparative Approach

All mammals begin life in social groups, but for some species, social relationships persist and develop throughout the course of an individual’s life. Research in multiple rodent species provides evidence of relatively conserved circuitry underlying social behaviors and processes such as social recognition and memory, social reward, and social approach/avoidance. Species exhibiting different complex social behaviors and social systems (such as social monogamy or familiarity preferences) can be characterized in part by when and how they display specific social behaviors. Prairie and meadow voles are closely related species that exhibit similarly selective peer preferences but different mating systems, aiding direct comparison of the mechanisms underlying affiliative behavior. This chapter draws on research in voles as well as other rodents to explore the mechanisms involved in individual social behavior processes, as well as specific complex social patterns. Contrasts between vole species exemplify how the laboratory study of diverse species improves our understanding of the mechanisms underlying social behavior. We identify several additional rodent species whose interesting social structures and available ecological and behavioral field data make them good candidates for study. New techniques and integration across laboratory and field settings will provide exciting opportunities for future mechanistic work in non-model species