Vasotocin is an oligopeptide homologous to oxytocin and vasopressin found in all non-mammalian vertebrates (including birds, fishes, and amphibians) and possibly in mammals during the fetal stage of development.

Arginine vasotocin (AVT), a hormone produced by neurosecretory cells within the posterior pituitary gland (neurohypophysis) of the brain, is a major endocrine regulator of water balance and osmotic homoeostasis and is involved in social and sexual behavior in non-mammalian vertebrates.

In mammals, it appears to have biological properties similar to those of oxytocin (stimulating reproductive tract contraction as in egg laying or birth) and vasopressin (diuretic and antidiuretic effects).

[6] The existence of two AVT preprohormones with different sequences in fishes (such as chum salmon, Oncorhynchus keta[7]) is evidence for gene duplication.

[8] AVT and synthetic analogs injected into monkeys cause reabsorption of osmotically free water and changes in excretion of sodium and potassium ions in the kidneys.

In laying hens, AVT synthesised in magnocellular diencephalic neurons is released into circulation in a highly coordinated manner, contributing to the peripheral control of oviposition.

The main findings of these studies have revealed that AVT plays an integral role in the pair bonding behavior and social hierarchy in non-mammalian vertebrates.

[11] A study that investigated the role of social construction and AVT compared territorial and non-territorial species of tropical coral reef fish.