Summary: Elie et al. (2010)

In birds, vocal duetting is a mutual acoustic joint display, usually made by a mated pair, of temporally coordinated vocalisations (vocal or nonvocal sounds). Elie et al. (2010) investigated whether private vocalisations between pairs of zebra finches (Taeniopygia guttata) could be considered vocal duetting. They recorded meeting sequences (vocal sounds made upon return to the nest) and sentinel sequences (vocal sounds made when one individual was outside the nest) to determine whether these sequences fitted the identified criteria for vocal duetting. They found that meeting sequences were more common when separation period increased, whereas sentinel sequences were more common when separation period decreased. For both sequence types, the number of female and male calls were positively correlated, indicating coordination between mates. Elie et al. (2010) propose that these private calls represent duets. Since partners performed coordinated mutual displays, mutual displays represent vocal duets and may function to mediate pair bond maintenance.

Summary: Clutton-Brock et al. (2006)

For most animals, competition is more intense in the sex that invests less in offspring. However, in some cooperatively breeding species, such as meerkats (Suricata suricatta), females (which normally invest more in care) compete more frequently and intensely. In the case of meerkats, a single dominant female will monopolise reproduction in a group. Clutton-Brock et al. (2006) showed that female meerkats gain greater reproductive benefits from acquiring dominance status and the traits that increase competitive ability also exerted a greater influence on breeding success. Individual differences in breeding success depend on the length of time the individual remains dominant in the group. Clutton-Brock et al. (2006) show that females that reach dominance status have longer breeding tenures and gain greater reproductive benefits than males. They suggest that the greater benefits accrued could explain why females compete so intensely for breeding opportunities. They suggest that the mechanism generating sex differences in reproductive competition in parental investment is not only related to sex differences in parental investment. They also suggest that competition for breeding opportunities influences the evolution of sex differences and how sexual selection operates.

Summary: Smith et al. (2002)

Humans have three types of cone receptor, while birds have four and are sensitive to ultraviolet light (UV). It is thus likely that birds require four primary colours for colour vision and are thus tetrachromatic. Like humans, birds have short, medium and long wavelength sensitive single cones. Birds use UV signals for a number of tasks, such as mate choice and foraging, but few studies have investigated a role for UV in the detection of chromaticity differences. Achromatic mechanisms are involved in the perception of brightness while chromatic mechanisms are responsible for the perception of colour differences. Smith et al. (2002) developed a 'colour blindness' test, which they administered to a passerine, the European starling (Sturnus vulgaris), and a non-passerine, the Japanese quail (Coturnix c. japonica). This was an associative learning technique where the bird had to learn to discriminate between patterns of random intensity with or without UV reflectance. Both species were able to distinguish between orange and red stimuli, and between UV and non-UV stimuli, and were making the discrimination using chromaticity differences, not achromatic cues. This indicates that the output of the UV cone is involved in chromatic colour vision.

Summary: Persaud & Galef (2005)

Generally, females invest more in their offspring than males, therefore they should be more choosy when selecting mates. Furthermore, in species where sexual coercion occurs, females may exert an influence on paternity by selectively voiding or retaining sperm of reproductive partners, which might affect their partner's reproductive success. This is known as postcopulatory or cryptic mate choice. Persaud & Galef (2005) tested whether male Japanese quail (Coturnix japonica) that are preferred by females have higher reproductive success (measured by likelihood of egg fertilization) than males that are not preferred by females. They also tested whether a male's reproductive success could be increased if a female observed him courting and mating with another female. They found that males that are preferred by females have a greater likelihood of fertilizing her eggs and that a female's preference could be enhanced by her observations of male mating behaviour. In addition, choosing a male that had courted and mated previously increased his likelihood of successfully fertilizing another female's eggs. Furthermore, females can identify males that are more likely to inseminate them and can exert a degree of control over which male will fertilize her eggs, thereby influencing both paternity and a male's reproductive success. The results suggest that female Japanese quail can exercise postcopulatory mate choice and that female preference can directly or indirectly affect a male's fertilization success.

Summary: Viellette & Reebs (2010)

Syrian hamsters (Misocricetus auratus) are used extensitvely in biomedical and behavioural research, but many aspects of hamster welfare remain open to study. Replacing soiled bedding is standard animal husbandry practice, but the how often this should be done is still questionable, as cage cleaning can induce stress. Veillette & Reebs (2010) tested whether Syrian hamsters prefer new bedding in contrast to soiled, lived-in bedding for nesting and they also assessed the relative value of shelters. They used 15 male and 15 female animals, none of which have previous experience with shelters. Most male and female hamsters favoured the old cage over the new, regardless of the presence of a shelter, and the majority of male hamsters (and some females) never nested in the new cage. Their results suggest that nesting hamsters show low motivation for a cage with new bedding and they value shelters. Veillette & Reebs (2010) indicate that the standard husbandry practice of weekly cleaning may only be justified on the basis of sanitary and health considerations.