Echolocation in the large molossid bats Eumops glaucinus and Nyctinomops macrotis

Area of Science:

• Zoology
• Bioacoustics
• Ecology

Background:

• Eumops glaucinus and Nyctinomops macrotis are the largest molossid bats in Cuba.
• Both species share the same ecological guild and similar body size.
• Large body size in bats often correlates with low-frequency echolocation calls.

Purpose of the Study:

• To investigate and compare the echolocation inventories of Eumops glaucinus and Nyctinomops macrotis.
• To test predictions from the "vocal plasticity hypothesis" and the "scaling hypothesis" regarding echolocation call overlap.
• To determine if these bat species produce calls within the human audible range.

Main Methods:

• Recording and analyzing echolocation calls emitted by Eumops glaucinus and Nyctinomops macrotis during hunting.
• Comparing acoustic parameters such as call design, duration, slope, bandwidth, and spectral characteristics.
• Statistical analysis of differences in search calls between the two species.

Main Results:

• Echolocation repertoires of both species were found to be very similar and of low frequency.
• Most differences between the species were observed in their search calls.
• Statistical differences in search calls support the "scaling hypothesis" given the slight size difference between E. glaucinus and N. macrotis.
• Both species emit echolocation calls below 20-25 kHz, placing them in the human audible range.

Conclusions:

• Eumops glaucinus and Nyctinomops macrotis exhibit significant overlap in their echolocation inventories, consistent with theoretical predictions.
• The low-frequency echolocation calls of these large molossid bats are unique in Cuba for being audible to humans.
• This study highlights the interplay between body size, vocal plasticity, and echolocation call characteristics in closely related bat species.