LSM1303 Animal Behaviour Student Blog

Doesn't this baby mole look cute?

(image source: http://www.dirtdoctor.com/pics/content_img.2118.img.bmp)

Well, it grows up to look like this.

(image source: http://farm2.static.flickr.com/1128/554140889_72473dfcae.jpg)

This is the star-nosed mole, found in wetlands and marshes in the West, and recent studies have found that it is the fastest eating mammal in the world. The most interesting part of this animal is its nose, which consists of 22 extremely touch-senstive 'tentacles'. These are covered by "25,000 sensory receptors and contains 100,000 large nerve fibers - six times as many as an entire human hand". Its sensitive nose aids it in sensing, identifying and eating prey, and is so useful that the mole has gained the title of eating champion.

Here s a video to explain more:

Research has focused on the speed at which the star-nosed mole can handle food, even taking as little as one fifth of a second. The rate at which they can consume prey is very interesting for a number of reasons.

The first is the nature of the appendages themselves. Moles have extremely poor eyesight, but its nose seems to make up for this lack in vision, due to its sensitivity. It also acts as a 'hand' in grasping prey and putting them into its mouth. Its nose also has a very large surface area, with individual 'fingers' that aid it in pushing objects around at a faster rate. This implies that it can find a significantly larger number of small prey than other mammals without this type of nose, in a given period of time. Furthermore, the star-nosed mole’s brain may also have been evolved to become more efficient. This is demonstrated by the fact that "all mammal brains represent the information that comes from touch-sensitive maps of the body”. While other moles have two of these maps of their nose, star-nosed moles have three. This results in its greater overall effectiveness.

Star-nosed moles move "almost at the speed limit set by its brain and nervous system". They practically utilize the maximum potential of its brain, and this enables them to work very swiftly. This gives them a competitive advantage over other animals, by factoring in prey profitability. This is the "ratio between the energy a predator gains from eating a prey animal and its “handling time,” where handling time is defined as the time between detecting an animal and eating it. According to the prey profitability formula, by reducing its handling time to a fraction of a second, the star-nosed mole can gain energy from chowing down on small insect larvae, tiny worms and other small food sources. Predators that take a few seconds to handle each prey animal, on the other hand, actually use more energy in the process of catching and eating such small prey than they gain from eating it". This clearly illustrates the extent of how beneficial its nose can be, by allowing to mole to be very energy-effective, expending less energy than it takes in from eating small prey.

Star-nosed moles live in wetlands and marshes, and this is why only this particular mole has this sort of nose. The soil found in wetlands is damp compared to dry soil, and contain a multitude of small insect larvae. As aforementioned about prey profitability, these collectively provide energy for the star-nosed mole, because it only expends a small amount of energy on locating them. Moreover, wetlands also have damp soil that would not damage their sensitive noses.

The star-nosed mole clearly illustrates how eating behaviours can be adaptive in the grand scheme of evolution. In addition, it shows how selective and specific these behaviours may be, as they particularly cater to the needs of the animal.

If you'd like to learn more, you can go to the star-nosed mole theatre here.

References:

"Star-nosed mole has moves that put the best magician to shame," by David F. Salisbury. Exploration, 2 February 2005.

"Underground Gourmet: Mole Sets a Speed Record," by Carl Zimmer. The New York Times, 8 February 2005.