Postpartum depression is a serious mental health condition that affects female humans following childbirth – resulting in anxiety, despair and isolation. Other primate species appear to experience similar states, according to some studies. New research published in the journal PeerJ Zoological Science in January 2026 suggests that female howler monkeys turn to botanical solutions for relief.
The authors of the paper focused on a population of mantled howler monkeys (Alouatta palliata mexicana) on Agaltepec Island in Mexico. The monkeys eat mostly fruits and leaves but supplement their diet with flowers during the blooming seasons of the trees they inhabit. According to the study, lactating females – those that had given birth and were rearing young – increased their consumption of flowers.
“This is notable because the consumed flowers are rich in flavonoids, especially flavanones and flavones,” said lead author Anna Gisbrecht, who conducted the research as part of her PhD at the Institute of Neuroethology at the University of Veracruz.
“These compounds have been shown to exhibit antidepressant and anxiolytic effects in humans and animal models, acting in ways similar to progesterone and estrogen [oestrogen] hormones that drop sharply after birth.”
The researchers observed the monkeys eating flowers from five species of tree: Andira galeottiana, Bursera simaruba, Dendropanax arboreus, Gliricidia sepium and Spondias mombin. The blossoms of all five species were high in flavanones and three were high in flavones. Flavanones and flavones belong to a group of chemicals produced by plants called flavonoids. The flowers also contained tannins.
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Both flavonoids and tannins are part of a larger family of chemical compounds known as polyphenols. Flavonoids have been used experimentally in treating human postpartum depression. Interestingly, female monkeys later in their lactation phase were more inclined toward flowers heavy in tannins – other animals eat tannin-rich plant material to increase lactation.
“It is important to clarify that the idea of mood regulation through food consumption remains a working hypothesis that requires further investigation,” cautions Gisbrecht.
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The researchers were unable to obtain physical samples from the monkeys, so their results are purely observational. That is to say: they recorded female monkeys eating extra flowers but were unable to measure hormone levels using blood or faecal material. Nonetheless, their hypothesis strongly correlates to a wide array of findings indicating medicinal use of plants and other substances by non-human animals.
Many other species appear to self-medicate using natural compounds, from South American parrots that flock to mineral deposits for their anti-parasitic properties to elephants that apply plants to wounds and even use them to induce labor.
