Modified Whiskers Handle Food

close up photo of gray manatee underwater

Biological Strategy

Florida manatee

Jeanette Lim

Image: Benjamin Brandt / Pixabay / Free non-commercial use

Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Distribute Solids

Solids include resources such as food, seeds, spores, and leaves, which living systems must sometimes move to accomplish various activities such as pollinating, feeding their young, or building shelters. To effectively distribute solids, living systems must use strategies appropriate to the sizes and types of solids and the media in which they exist (air, water, or another medium). This may entail strategies beyond simply holding and carrying solids. For example, some seeds are carried by the wind to new locations for germination. Others–like the burdock plant’s hooked seeds–cling to animal fur to be transported.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Modified whiskers of the Florida manatee capture and handle food with the help of finely controlled lips.

Whiskers are a familiar sight on mammals. Also called vibrissae, they’re commonly found on the face and used to sense tactile cues from the physical world around a mammal. The Florida manatee is an aquatic mammal that has vibrissae all over its body, but especially concentrated on the face and near the mouth. The vibrissae on its lips are modified into short, stiff bristles that appear to have a unique function among mammals: they’re primarily used to capture and handle food and other objects.

The Florida manatee’s muscular lips have a special shape and are capable of fine controlled movements. The upper lip is shaped like a plump U, with the ends pointing back toward the mouth and bearing tufts of stiff vibrissae. The bottom lip is round and also bears bristles. When feeding on submerged plants (manatees are herbivores), the manatee brings the ends of its upper lip together and extends the bristles, which grab the plant and direct it toward the mouth. The upper lip then spreads back out and the lower jaw closes, pushing the plant farther into the mouth. When feeding on floating plants, the upper lip is first used like a rake. The manatee extends its upper lip over the floating plant and repeatedly rakes it towards its mouth using the lip’s bristles.

Other parts of the Florida manatee’s snout is covered in vibrissae that are highly sensitive to touch. These enable the manatee to sense and explore food and objects before using its bristly vibrissae to grasp them. Having such a sensitive and finely controlled system for gathering food likely helps manatees efficiently feed on a variety of aquatic plants at different locations in the water column.

Image: Keith Ramos / USFWS / CC BY - Creative Commons Attribution alone

Image: Tracy Colson / USFWS / CC BY - Creative Commons Attribution alone

Last Updated June 28, 2017

References

“Florida manatees possess an unusually large degree of fine motor control of the snout and perioral bristles. The large and robust perioral bristle fields of the upper lip were used in a prehensile manner during feeding. Bristle use by manatees feeding on submerged vegetation differed from that seen during feeding on floating vegetation. Other behavioral use of the perioral bristles shows variation depending upon the situation encountered. The degree of plasticity of perioral bristle use supports our hypothesis that the vibrissal-muscular complex of the Florida manatee has evolved to increase the efficiency of grazing and browsing on aquatic vegetation and to fully maximize the potential of the manatee as a generalist feeder.” (Marshall et al. 1998a:274)

Journal article