A blind climber: The first evidence of ultrasonic echolocation in arboreal mammals.

Author: Panyutina AA1,2, Kuznetsov AN2, Volodin IA2,3, Abramov AV4,5, Soldatova IB2
1Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia.
2Department of Vertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
3Scientific Research Department, Moscow Zoo, Moscow, Russia.
4Zoological Institute, Russian Academy of Sciences, Saint Petersburg, Russia.
5Joint Vietnam-Russian Tropical Research and Technological Centre, Hanoi, Vietnam.
Conference/Journal: Integr Zool.
Date published: 2017 Mar
Other: Volume ID: 12 , Issue ID: 2 , Pages: 172-184 , Special Notes: doi: 10.1111/1749-4877.12249. , Word Count: 222

The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis, a poorly known enigmatic semi-fossorial semi-arboreal rodent. Data on eye structure are presented, which prove that Typhlomys (translated as "the blind mouse") is incapable of object vision: the retina is folded and retains no more than 2500 ganglion cells in the focal plane, and the optic nerve is subject to gliosis. Hence, Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation. Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis. The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession. Structurally, these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species, but they are too faint to be revealed with a common bat detector. When recording video simultaneously with the ultrasonic audio, a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated. Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the "echolocation-first theory" of pre-flight origin of echolocation in bats.

© 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

KEYWORDS: Rodentia; Typhlomys; arboreal locomotion; reduced eyes; ultrasonic echolocation

PMID: 27991725 DOI: 10.1111/1749-4877.12249