Mammalian Senses

Mammalogy (Spring 2014 Althoff - reference FDVM Chapter 8)

LEC 09

Senses

• Well-developed compared to most all other classes (i.e., fishes, reptiles, etc.)

• Key to “_____________” resourcea) find prey (predators)b) find forage (prey) in form of seeds,

grasses, forbs• Key to being “had” by predator including

humans

Senses…con’t• Sight: probably ____ superior to birds,

specifically when compared to raptors• Hearing: probably ____ superior to birds.

(exception: echolocation)• Touch: ______ superior to birds• Smell: _____ superior to birds

_____________vertebrate brain

forebrain midbrain hindbrain

embryonic vertebrate brain frog

human goosecerebellum

cerebrum

bird sheep

Items to note here: 1) ________ proportion of cerebellum to

cerebrum 2) ______—present (mammal) vs . absent

(bird)—in the cerebrum exterior

SOU

RCE:

Fish

beck

and

Seb

astia

ni (2

008)

Fig

. 12.

3

Types of Sensory Receptors• _________________ (taste, smell)• _________________ (touch, hearing)• _________________ (sight)• _________________ (touch, pain)

Smell• Acute • Development of turbinal bones (tubinates)

in nasal cavities (___________________ ________)

• Well developed olfactory bulbs(bulla) in insectivores, carnivores, &

rodents• Olfactory bulbs and lobes, great portion of

brain• Primates have reduced nasal capacity

• Some sensitivities up to 1 million trillion (1015) part of air

• Mammals…with very highly developed olfaction…aided by presence of ________: thin bone lined with olfactory epithelium

• vomeronasal organ(Jacobson’s

organ)

Olfactionmaxilloturbinates

GENERALIZED MAMMAL CONDITION

UNGULATE CONDITION

vomeronasal organ

Cutaway view of nasal chamber of Abert’s squirrel (Sciurus aberti)

presphenoidbone

frontal bone

frontal bonecribiform platemesethmoid

nasal

premaxillarymaxillarypalatine

Smell...con’t

• Smell accomplished throughchemoreceptors (broad range of these):

a) humans: ____ millionb) dog: ____ million

• Receptors detect food, predators, prey, and status of conspecifics

Smell...con’t

• Olfactory “hairs” (dendrites) connect to olfactory receptors which connect to olfactory bulb

• Receptor cells actually in ___________ ___________

To __________lobe in brain

olfactoryepithelium

olfactory ciliaof olfactory cell

“non-sensory”part

Smell...con’t

• Evidence for rodents (& mammals in general likely) to detect:a) sex of conspecificb) maturity of conspecificc) _________________ heritaged) _______________e) “social” status

• Important in _________________

Hearing• Well developed in most species (as

indicated by _____ of auditory bulla)

• ___________ of vertebrate animals to have this much dependency on

sense of hearing• Only class with ______________

(pinna) to funnel sound

Hearing...con’t• External auditory meatus--tube

leading from pinna to tympanicmembrane--is usually long in mammals

• Middle ear is air-filled chamber that houses three ossicles (hammer anvil stirrup)

(malleus incus stapes)

FDVMK Fig. 8.2 p146

Hearing...con’t

• Size of auditory bulla can reflect animals ability to pick-up low frequency (1-3 MHz) sounds

• Ex: Kangaroo rata) ___________________b) ____________________ ____________________

FDVMK Fig. 18.10 p354

Kangaroo rat (Dipodomys)

Auditory bulla is, on the average, larger in _____________________. Sound is known to be absorbed to different degrees under different temperature and humidity conditions. An enlarged bullae may _______________ for poor sound-carrying qualities of warm, dry, desert air

Echolocation

• _____ of all mammals use _____________ orientation forsensing surroundings (bats,shrews, cetaceans)

• Bats have overcome “darkness” with development of echolocation

Echolocation...con’t

• Microchiropterans pretty much have abandoned vision in favor of echolocation

• Echolocation: ultrasonic pulses are emitted by bats, pulses reflected back objects

• Not confirmed until 1940’s

Echolocation...con’t• For bats, not only is prey detected, but

communication with conspecifics is achieved

• Vocalizations produced by larynx emittedthrough nose or mouth

FDVMK Fig. 13.8 p263

Echolocation: INFORMATION GAINED

of target

of the target

of the target

of the target

1

2

3

4

Echolocation...con’t

• Humans can hear _____ kHz(20,000 cycles per second)

• Bats emit _______ kHz pulses with very _____ wavelengths...this

range results in detect of prey closest to the size that a bat species can handle

Echolocation...con’t

• Different species of bats emit different ranges of pulses--able to __________________ now by recording pulse rate & duration

• ______ also, apparently, able todetect bat sounds to some degree…version of “___________________”

References on bat foraging & detection of different species:

Adam, M.D., M.J. Lacki, and T. G. Barnes. 1994.Foraging areas and habitat use of the Virginia big-eared bat in Kentucky. J. Wildlife Management 58:462-469.Krusic, R.A., M. Yamaski, C.D. Neefus, and P.J.

Pekins. 1996. Bat habitat use in WhiteMountain National Forest. J. Wildlife.

Management 60:625-631.

Sight: eye proportional differences(specifically in the _______)

FDVMK Fig. 8.1 p145

d = dorsal side of eyeball v = ventral side (bottom)n = nasal (nose) side of eyeball t = temporal (outer side)c = cornea l = lens (shaded-tan)

Sight

• Most mammals have well-developed ___________________ ...this is a reflective

structure within the choroid that improves night vision by reflecting light back to the retina

Sight...con’t• Tapetum lucidum

a) results in “________”b) some species can have

different color of eye shine• _____ vs. ______ photoreceptors

Rods

• Very sensitive to _____ light• Contribute to “coarse” vision

--detection of movement by detecting changes in

light intensity--good night-time

vision • Contain molecules of ______________

Rods...con’t• Rhodopsin breaks down with light

absorption, result is _________ changes across the rod membrane which, in turn, influence neurons.

• _________ rods than cones in __________ species

CHOROID

To occipital lobe in brain

Conecell

Rodcell

Rod

mem

bran

e

Lightrays

Cones

• Stimulated by _________ light levels• Densely packed in fovea where nerve

tissue is thinner• Contribute to “precise” _____________

between adjacent points in space

Cones...con’t

• Pigments in different cone cells aresensitive to wavelengths

corresponding to red, green, and blue colors

• More abundant in diurnal species, but--even for those--______ as much

as birds

Up to present day, only three mammalian groups again developed retinas dominated by cones:A) SCIURID RODENTS, B) TUPAIAS (tree shrews) and C) (DIURNAL) PRIMATE GROUPS

European Ground Squirrel Citellus citellus

This stained semi-thin section shows the photoreceptor mosaic.A few rods are present but not well distinguishable atthis level of sectioning. In the ground squirrel retinas (also the Alpine marmot for example) they are a small minority (5%). Otherwise, apparently there are two types of cones.

A) subpopulation of larger darker staining cells are the short wavelength sensitive (Blue or S-) cones. They establish a regular sub-mosaic of ca. 10%.

(and they are apparently ________________)

B) Other cells are mostly (>80% )long wavelength sensitive or "Green" cones.

European Ground Squirrel Citellus citellus

Regardless of number of cones and rods, object ____________ still can be _____________

___________ intypes of photoreceptors…including types of cones

1

2

What some mammals might see…

• http://premiumblend.net/2009/08/21/how-dogs-see-colors/

Human Dog

Sight...con’t

For the most part, then, most mammals probably “see” black-and-white” but there is a ________ _______________ for those with well-developed sight

(excludes microchiropterans, moles, shrews, etc.—who have really poor eyesight)