Uncovering maternal to paternal communications in mice

Researchers at Japan’s Kanazawa University have proven the existence of communicative signalling from female mice that induces male parental behaviour.

Most mammalian parents use communicative signals between the sexes, but it is uncertain whether such signals affect the levels of parental care in fathers. Scientists have long suspected that female mice play a definite role in encouraging paternal relationships between male mice and their pups.

Now, a research team at Kanazawa University led by Haruhiro Higashida in collaboration with scientists across Japan, Russia and the UK, have proven the existence of auditory and olfactory (smell) signals produced by females which actively trigger paternal activity in males.

Higashida and his team conducted a series of experiments with females and males living in established family groups. Pups were removed from the cage for a short time, while one or both parents remained in the nest. The pups were then returned to the cage, away from the nest. Lone females nearly always brought the pups back to the nest, but lone males were less likely to do so.

Most interestingly, the researchers showed that males were much more likely to retrieve pups when they remained with their mate. This behaviour may be related to ultra-sonic noises emitted by females under stress. These sounds are not emitted by males, pups or non-parental females, and they encouraged the males into parental behaviours. The females also released olfactory signals in the form of pheromones, which triggered the same reaction in the males.

Higashida and his team are keen to expand on their results by analyzing neural signalling in the male brain in response to these female communications.

The Persistence of Memory in Mice

It’s frequently said that scent is the sense most powerfully tied to memory. For mice, it turns out, that’s especially true—at least when it comes to a sniff of the urine of potential mates.

According to a study published in Science by researchers from the University of Liverpool, female mice exposed to the potent pheromone darcin (found in male mouse urine) just a single time will repeatedly return to the exact site of exposure up to 14 days later, even after the pheromone is taken away.

“We have shown that a male sex pheromone in mice makes females …remember exactly where they encountered the pheromone and show a preference for this site for up to two weeks afterwards,” said lead author Sarah Roberts in a statement. “Given the opportunity, they will find that same place again, even if they encountered the scent only once and the scent is no longer there.”

“This attraction to the place they remember is just as strong as attraction to the scent itself,” said co-author Jane Hurst. “Darcin, therefore, induces mice to learn a spatial map of the location of attractive males and their scents, to which they can easily return.”

The researchers determined that the important factor was the pheromone darcin because the same results occurred when a synthetic version of the chemical was put into a petri dish on its own. Additionally, when the female mice were exposed to female urine instead, there was no indication of a preference, because darcin isn’t present in the females’ urine.

Interestingly, the pheromone also produced a powerful effect on another group of mice: competitor males. When they were used in the same experiment, they also demonstrated a preference for the place where they remembered smelling other males’ urine, but they didn’t show this type of spatial memory when the urine used was their own. The researchers speculate that this is because of a motivation to linger near the site and mark the territory with their own pheromone scent, to advertise their availability to female mates.

The scientists speculate that this lingering affinity for the memory of urine is used by the mice as a mental shortcut for finding mates. In a natural setting (instead of cages), rather than having to smell the pheromones from a distance and then track them to the source, they can simply camp out by urine deposited by a potential mate and wait for their likely return.

How Random Is Social Behaviour? Disentangling Social Complexity through the Study of a Wild House Mouse Population

Out of all the complex phenomena displayed in the behaviour of animal groups, many are thought to be emergent properties of rather simple decisions at the individual level. Some of these phenomena may also be explained by random processes only. Here we investigate to what extent the interaction dynamics of a population of wild house mice (Mus domesticus) in their natural environment can be explained by a simple stochastic model. We first introduce the notion of perceptual landscape, a novel tool used here to describe the utilisation of space by the mouse colony based on the sampling of individuals in discrete locations. We then implement the behavioural assumptions of the perceptual landscape in a multi-agent simulation to verify their accuracy in the reproduction of observed social patterns. We find that many high-level features – with the exception of territoriality – of our behavioural dataset can be accounted for at the population level through the use of this simplified representation. Our findings underline the potential importance of random factors in the apparent complexity of the mice’s social structure. These results resonate in the general context of adaptive behaviour versus elementary environmental interactions.

Singing Mice Show Signs of Learning

Guys who imitate Luciano Pavarotti or Justin Bieber to get the girls aren’t alone. Male mice may do a similar trick, matching the pitch of other males’ ultrasonic serenades. The mice also have certain brain features, somewhat similar to humans and song-learning birds, which they may use to change their sounds, according to a new study.

"We are claiming that mice have limited versions of the brain and behavior traits for vocal learning that are found in humans for learning speech and in birds for learning song," said Duke neurobiologist Erich Jarvis, who oversaw the study. The results appear Oct. 10 in PLOS ONE and are further described in a review article in Brain and Language.
[Arriaga, G. et. al. (2012) “Mouse vocal communication system: are ultrasounds learned or innate?”  Brain and Language]

The discovery contradicts scientists’ 60-year-old assumption that mice do not have vocal learning traits at all. “If we’re not wrong, these findings will be a big boost to scientists studying diseases like autism and anxiety disorders,” said Jarvis, who is a Howard Hughes Medical Institute investigator. “The researchers who use mouse models of the vocal communication effects of these diseases will finally know the brain system that controls the mice’s vocalizations.”