Discover Nature’s Pharmacy: How Animals Heal Themselves with Earth and Coral

[Column “ Brilliant Animals “] We’ve been told since ancient times: fish have short memories, birds have tiny brains, and bears are exceptionally cruel… Yet, scientific studies continue to accumulate, showing that non-human animals possess intelligence, sensitivity, and ingenuity. Each month, Decatur Metro offers a collection dedicated to these fascinating creatures.

During her multi-year dives in the Red Sea, biologist Angela Ziltener from the University of Zurich made a remarkable discovery. Several meters underwater, she repeatedly observed Indian Ocean dolphins (Tursiops aduncus) lining up to rub against corals and sponges.

This behavior appears to be intentional: the dolphins rub different corals with specific parts of their bodies, avoiding others… By scratching against these surfaces, they release mucus from the corals, which coats their skin in a yellowish or greenish hue. Younger dolphins first watch their elders and then replicate the behavior.

To understand why dolphins engage in this rubbing, Angela Ziltener, with the help of chemist Gertrud Morlock, analyzed the mucus produced by their three favorite ‘scratching posts’: two corals (Rumphella aggregata and Sarcophyton sp.) and a sponge (Ircinia sp.). Their findings were published in 2022.

The analyzed sponges and corals contain seventeen chemical compounds with antibacterial, antioxidant, or hormonal properties that could potentially heal skin conditions. Dolphins are known to be susceptible to poxvirus infections (which cause skin lesions) and fungal diseases.

Is it merely play ? Self-massage ? A deliberate healing technique ? The debate is still ongoing. « This is very valuable work », said a primatologist who is among the leading experts in animal self-medication. While it’s well-documented that terrestrial non-human animals self-medicate, from butterflies to birds to chimpanzees, much remains to be discovered in the ocean, a much less accessible field, explained biologist Jaap de Roode to Decatur Metro recently.

From grandmothers to granddaughters, we share recipes — not scientifically supported — like ginger for first-trimester nausea and raspberry leaf tea to prepare for childbirth. In Madagascar, female sifakas, large lemur-like dancers, rely on fihamy and kily, according to a 2003 study published in the journal Primates.

Researchers observed that in the weeks before giving birth, these females consume much more of these plants, which are particularly high in tannins. Surprisingly, these molecules are produced by plants to deter herbivores because they are toxic in high doses. « Sifakas are doing something counterintuitive », said a researcher from Kyoto University.

Why take such a risk ? Researchers suggest several hypotheses. In other mammals, small amounts of tannins help fight certain parasites and stimulate milk production. Veterinarians also use them to prevent some miscarriages. Scientists have noted that females consuming these plants seem to experience fewer pregnancy failures than those that do not, although the exact mechanisms behind this consumption are not fully understood.

This behavior is not unique. A pregnant African elephant was observed in Kenya consuming leaves of Cordia goetzei Gürke to induce labor.

To recover from an overly rich meal, one might opt for broth, a salad, or… soil, if one is a Barbary macaque. In a study, researchers observed for the first time a population of this species practicing geophagy — the deliberate consumption of soil — near Gibraltar.

According to Sylvain Lemoine, co-author of the study and a primate behavior specialist at the University of Cambridge, these monkeys might use this practice to rebalance their intestinal microbiota (i.e., the populations of microbes living in their digestive tract) disrupted by the ultra-processed snacks given by tourists.

« We believe that junk food consumption disrupts the microbiota composition, and we know that the bacteria and minerals in the soil can help rebalance it », he explained.

Observations show that the macaques living near the Rock of Gibraltar (a tourist hotspot) are more than twice as likely to eat peanuts, ice cream, and other sweets. They are also the biggest consumers of soil in the territory. In winter, when tourist numbers decrease, junk food consumption drops by 40 %, and soil consumption by 30 %.

Other primates — like chacma baboons in South Africa — eat soil to detoxify their bodies. However, for the Barbary macaques, this strategy could have unintended consequences. The soil they consume is often taken from areas near roads, thus potentially polluted.

The author of these lines comes from Savoie, where a little sugar soaked in a 69-degree plant-based “invigorating” monastic elixir was reputed to cure all ailments. Skeptical ? You might be right. Yet, bees experience the beneficial effects of a (small) dose of ethanol. According to a 2025 study published in Behavioral Ecology, worker bees infected with an intestinal parasite more often choose to consume nectar containing a bit of ethanol than their healthy counterparts.

To reach this conclusion, researchers raised over 3,000 bees in a laboratory, then gave them a choice between a classic sweet solution and another containing just 0.5 % or 1 % alcohol, concentrations similar to those found naturally in some fermented nectars. Verdict: bees infected by Nosema ceranae, a parasite that attacks their intestines, were 26 % more likely to choose the alcoholic drink.

Alcohol is not without risks. At 1 %, it increases the mortality of healthy bees. However, this harmful effect is significantly less pronounced in sick bees. However, it does not reduce the number of parasites in their bodies. Scientists therefore see this as a possible case of self-medication, although they remain cautious. Perhaps ethanol rather improves their intestinal function or microbiota, or alters their immune response. Another more worrying hypothesis is that the parasite itself manipulates the dietary preferences of its host.