The desire to understand how the brain generates and patterns behavior has driven rapid methodological innovation in tools to quantify natural animal behavior. While advances in deep learning and computer vision have enabled markerless pose estimation in individual animals, extending these to multiple animals presents unique challenges for studies of social behaviors or animals in their natural environments. Here we present Social LEAP Estimates Animal Poses (SLEAP), a machine learning system for multi-animal pose tracking. This system enables versatile workflows for data labeling, model training and inference on previously unseen data. SLEAP features an accessible graphical user interface, a standardized data model, a reproducible configuration system, over 30 model architectures, two approaches to part grouping and two approaches to identity tracking. We applied SLEAP to seven datasets across flies, bees, mice and gerbils to systematically evaluate each approach and architecture, and we compare it with other existing approaches. SLEAP achieves greater accuracy and speeds of more than 800 frames per second, with latencies of less than 3.5 ms at full 1,024 × 1,024 image resolution. This makes SLEAP usable for real-time applications, which we demonstrate by controlling the behavior of one animal on the basis of the tracking and detection of social interactions with another animal.

In many vertebrate species, certain individuals will seek out opportunities for aggression, even in the absence of threat provoking cues. While several brain areas have been implicated in generating attack in response to social threat, little is known about the neural mechanisms that promote selfinitiated or "voluntary" aggression seeking when no threat is present. To explore this directly, we utilize an aggression-seeking task wherein male mice can self-initiate aggression trials to gain brief and repeated access to a weaker male that they attack. In males that exhibit rapid task learning, we find that the ventrolateral part of the ventromedial hypothalamus (VMHvl), an area with a known role in attack, is essential for aggression seeking. Using both single unit electrophysiology and population optical recording, we find that VMHvl neurons become active during aggression seeking and their activity tracks changes in task learning and extinction. Inactivation of the VMHvl reduces aggression-seeking behavior, whereas optogenetic stimulation of the VMHvl accelerates moment-to-moment aggression seeking and intensifies future attack. These data demonstrate that the VMHvl can mediate both acute attack and flexible seeking actions that precede attack.Individuals may seek out opportunities to attack, even in the absence of overt threat 1 -9 . In the wild, male mice exhibit stalking behavior if they suspect foreign encroachment 10 , and Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use

Maternal care, including by non-biological parents, is important for offspring survival1–8. Oxytocin1,2,9–15, which is released by the hypothalamic paraventricular nucleus (PVN), is a critical maternal hormone. In mice, oxytocin enables neuroplasticity in the auditory cortex for maternal recognition of pup distress15. However, it is unclear how initial parental experience promotes hypothalamic signalling and cortical plasticity for reliable maternal care. Here we continuously monitored the behaviour of female virgin mice co-housed with an experienced mother and litter. This documentary approach was synchronized with neural recordings from the virgin PVN, including oxytocin neurons. These cells were activated as virgins were enlisted in maternal care by experienced mothers, who shepherded virgins into the nest and demonstrated pup retrieval. Virgins visually observed maternal retrieval, which activated PVN oxytocin neurons and promoted alloparenting. Thus rodents can acquire maternal behaviour by social transmission, providing a mechanism for adapting the brains of adult caregivers to infant needs via endogenous oxytocin.

Tinbergen proposed that instinctive behaviors can be divided into appetitive and consummatory phases. During mating and aggression, the appetitive phase contains various actions to bring an animal to a social target and the consummatory phase allows stereotyped actions to take place. Here, we summarize recent advances in elucidating the neural circuits underlying the appetitive and consummatory phases of sexual and aggressive behaviors with a focus on male mice. We outline the role of the main olfactory inputs in the initiation of social approach; the engagement of the accessory olfactory system during social investigation, and the role of the hypothalamus and its downstream pathways in orchestrating social behaviors through a suite of motor actions.