25 years studying a remarkable mammal - the star-nosed mole
By Kevin Campbell, University of Manitoba
Seeing a star-nosed mole in person is special. Discovering new insights into the biology of this remarkable species is even more so. Documenting these behaviours with the BBC Natural History Unit for a Sir David Attenborough series is icing on the cake! I was thus thrilled by the prospect of working with the BBC (for the 3rd time!) in 2022, to record the star-nosed mole’s underwater biology in unprecedented detail for their latest series - Mammals.
But my passion for this remarkable species began over 25 years ago.
It started back in 1995, with a number of chance events while researching muskrats as a graduate student at the University of Manitoba. With the aim of putting off grading lab reports one day, I paged through an issue of the Journal of Mammalogy. Here I came across the obituary for Cornell biologist William J. Hamilton Jr., who, as it turned out, studied star-nosed moles during his Ph.D. and published a paper on their natural history in 1931. Aware that this conspicuous but highly elusive species was both semi-aquatic and found in Manitoba. I promptly went to the library to read it. Quickly entranced, and wanting to learn more, I began amassing every publication I could find on the species.
Upon completing my Ph.D. a few years later, my thesis advisor offered to hire me for 6 months to do research on a topic of my choosing. Knowing that there was almost nothing known about the energetics, thermal biology and diving physiology of star-nosed moles, I informed him that I wanted to study them. He was skeptical that I would be able to find any, and suggested I consider another species. But, I was persistent! What we found during our research, was fascinating.
Although amazed by their rapid frenetic behaviour and seemingly unending pursuit of food, we were still shocked to discover that they could eat up to 15% of their body weight in just 10 minutes (more impressively, Vanderbilt University researcher Ken Catania told me that lactating females can eat up to 50 large Lumbricus earthworms – about 5 times their body weight – per day!).
Even more astonishing was finding that ingested food particles would start being defecated in as little as 8 minutes!
Even more astonishing was finding that ingested food particles would start being defecated in as little as 8 minutes!
We were also impressed with how well they could dive. However, we noticed that air-bubbles would often ‘escape’ from their elaborate nose while probing along the waters’ bottom.
We thus initially suspected these blind mammals were using ultrasonic bursts for navigation, though our experiments failed to find any evidence for this.
Fortunately, Ken Catania was studying the incredible somatosensory (touch) biology of the mole’s nose around this same time and, with the aid of a high-speed camera, demonstrated that they were instead inhaling and exhaling bubbles (‘sniffing’) to help track and identify aquatic prey items, as we were excited to show in the BBC Mammals series.
As I began focusing my research more and more on haemoglobin (including that of the iconic woolly mammoth) over the ensuing years, I was unsure I would ever study star-nosed moles again. But, one piece of the puzzle was left unanswered, and one that I long wondered about; how is the mole’s nose able to maintain the exquisite sense of touch needed to navigate and capture prey while foraging under the ice during a cold Canadian winter, when my fingers quickly go numb?
Working with the BBC again in 2022, provided the perfect opportunity to finally get some insights into this question. This collaboration led me and colleague Glenn Tattersall (Brock University) to the surprising discovery that the mole's nose is not only much colder than the rest of its body, but that it closely tracks the temperature of the water (or air) it is in, presumably to minimise costly heat loss; it remains a mystery how the ultra-sensitive touch receptors on the mole's nose appear unaffected by such large and rapid changes in temperature.
Now that this study is published, who knows, maybe the BBC will be interested in documenting this biological quirk with cutting-edge thermal camera technology next time…!
The star-nosed mole
A star-nosed mole uses its sensitive nose to hunt both underground and underwater.
