Hear! Hear! Here's to lemur ears!

by Dr. Sarah Zehr
We often make the assumption that the animals around us hear things in the same way we do, yet there are common examples that show that they don’t. The animal known as the human teenager, for example, with its young ears can hear a cell phone ringtone that is at a frequency that most adults, with their aging ears, cannot hear. What, then, does an animal of an entirely different species hear? Marissa Ramsier and Andy Cunningham, of Nate Dominy’s lab at UC Santa Cruz wanted to know. Having already studied the hearing of many other primate species, a trip to the DLC was obviously in order to find out how prosimian primates hear. They made multiple visits and tested the hearing of many of our species, including both nocturnal and diurnal animals. They are still analyzing their data, which should provide an interesting complement to the many vocalization studies that have been conducted over the years.
Of course we care about lemurs in general, but this project also made some fascinating discoveries about some of our individual animals in particular. First, as any of you who have been on the tour path know, the air handling unit by the main building can be quite loud. We were concerned that being near it constantly may have damaged the hearing of animals who live in nearby enclosures. So we tested their hearing. Much to our relief, there were no differences between their hearing and the hearing of other animals of the same species who do not live close to the air unit. It may be that the sound frequency of the equipment, which we find very loud and annoying, is not one that is as prominent in the range of hearing of lemurs.
Although there was no hearing loss in those lemurs, when the hearing of two of our lorises was tested (one slow loris, Lahkshmani, and one pygmy slow loris, Skimmer), they were found to be almost completely deaf! Which explained a lot. Such as why Lahkshmani, who is in our animal training program and is supposed to respond to a whistle, has been terrible at training. She simply couldn’t hear the signal. Knowing the auditory limitations of these two animals will allow us to better care for them. In addition, the fact that the only two animals to show significant hearing loss are lorises may be an indication that there is something interesting about their physiology. Or maybe it’s just coincidence. In any case, the moral of the story is that the research conducted here not only enlightens us about prosimians as a whole, but it can also help us learn about special characteristics of the animals who live at the DLC.