Male Woolly Mammoths Had Hormone-Fed Aggression Episodes

There really is no shortage of interesting courtship and mating rituals throughout the animal kingdom. From trilobite jousting to win a mate to giraffe’s all-important urine-sniffing rituals, doing so is serious business. And so is conquering a partner.

[Related: Male California sea lions have gotten bigger and better at fighting.]

For the first time, scientists have found direct evidence that adult male woolly mammoths experienced an event called a musth. Musth comes from the Hindi and Urdu word for intoxicated, and in the case of giant mammals like adult elephants, this is a testosterone-fueled event where the male sex hormone rises and aggression against rival males increases.

The study, published online May 3 in the journal Nature, found evidence that testosterone levels are recorded within the growth layers of elephant and mammoth tusks. In living male elephants, blood and urine tests detected elevated testosterone levels, but the musth fights of their extinct relatives have only been inferred from the fossilized consequences of testosterone-fueled fights, such as bits of tusk tips and skeletal injuries.

In the study, an international team of researchers reports the presence of annual testosterone surges (up to 10 times higher than baseline levels) within a woolly mammoth tusk preserved in permafrost.

The team took tusk samples from an adult African bull elephant from Botswana and two adult woolly mammoths: a male that roamed Siberia more than 33,000 years ago and an approximately 5,597-year-old female that was discovered on Wrangel Island. This island in the Arctic Ocean used to be connected to northeastern Siberia and is the last place where woolly mammoths survived until about 4,000 years ago.

“This study establishes that dentin is a useful reservoir for some hormones and sets the stage for further advances in the developing field of paleoendocrinology,” study co-author and paleontologist at the University of Michigan Museum of Paleontology said in a statement. , Michael Cherney. “In addition to the wide applications in zoology and paleontology, dental hormone records could support medical, forensic, and archaeological studies.”

Hormones are signaling molecules that help regulate physiology and behavior. Testosterone in vertebrate males is part of the group of steroid hormones. Testosterone circulates through the bloodstream and accumulates in various tissues.

[Related: How much acid should you give an elephant? These scientists learned the hard way.]

According to the authors, their findings demonstrate that steroid records in teeth can provide scientists with significant biological information that can even persist for thousands of years.

“Tusks hold particular promise for reconstructing aspects of mammoth life history because they preserve a record of growth in the dentin layers that form throughout an individual’s lifetime,” the study co-author said in a statement. and curator of the UM Museum of Paleontology, Daniel Fisher. “Because musth is associated with dramatically elevated testosterone levels in modern elephants, it provides a starting point for evaluating the feasibility of using conserved hormones in tusk growth records to investigate temporal changes in endocrine physiology.” .

Traces of sex hormones extracted from the tusk of a woolly mammoth provide the first direct evidence that adult males experienced mullence, an episode of increased testosterone-fuelled aggression against rival males. CREDIT: University of Michigan.

The team used CT scans to find the annual growth increments deep within the tusks, like tree rings. Modern elephant and ancient mammoth tusks are elongated upper incisor teeth, retaining only trace amounts of testosterone and other steroid hormones. All chemical compounds are incorporated into dentin, which is the mineralized tissue that forms the inside of teeth.

The study also called for new methods to extract steroids from tusk dentin using a mass spectrometer. Mass spectrometers identify chemicals by classifying the ions present by their mass and charge.

“We had developed steroid mass spectrometry methods for human blood and saliva samples, and have used them extensively for clinical research studies. But never in a million years did I imagine that we would be using these techniques to explore ‘paleoendocrinology,’” study co-author and UM endocrinologist Rich Auchus said in a statement.

The results and the new measurement technique will likely prompt new approaches to investigate reproductive endocrinology, life history, and even disease patterns in modern and prehistoric contexts.

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