A Microscopical Study of Exotic Animal Hairs: Part 2 (2024)

Kristen D. Wiley

Brookfield Zoo, Brookfield, Illinois, has been exceptionallycooperative and generous with the collection of hairs from an array ofanimals at their zoo. Several samples were examined and “AMicroscopical Study Of Exotic Animal Hairs: Part 1” was just the beginningof what could become lifelong work. Working with the Zoo has enabled McCroneAssociates to begin setting an exhibit in the Hamill Family Play Zoo,located within the Zoo, to teach guests how hairs appear when viewed througha microscope. This, hopefully, will allow younger generations to beginto appreciate the capabilities of the microscope. The exhibit will beinteractive, displaying a flip-book picturing reference samples, set nextto microscopes used to view the samples. The collection of hairs providedhas made it possible for McCrone Associates to take transmitted-lightphotomicrographs using plane-polarized light, fully-crossed polarizers,and scanning electron micrographs (SEMs), and make scale castings of theactual hairs.

In this follow-up to “A Microscopical Study Of Exotic Animal Hairs: Part 1”, the animals have been chosen at random. The BrownBear, Western Lowland Gorilla, and African Wild Dog are all on the endangeredspecies list. The Zoo is an active participant in the Species SurvivalPlan (SSP) for both the Western Lowland Gorilla and the African Wild Dog.The California Sea Lion, due to its protection by the Marine Mammal ProtectionAct of 1972, is not considered endangered. The Aardwolf is currently classifiedas rare.

Ursus arctos, commonly known as the Brown Bear,is found on three continents, making it the most widespread bear specieson Earth. Although its range is wide, its population numbers are stilllow. Brown Bears have been hunted, and their habitats have been overtakenby human expansion, which may explain why they are on the endangered specieslist. Their body color is usually dark brown, but can range in shadesfrom a cream-color to almost black. Some of their hairs may be tippedwith a whitish-silver color giving their coat a sheen-like appearance.

In Meltmount™ 1.662, you will notice a continuousmedulla in both transmitted light and with fully-crossed polarizers. Thissample has a stellate appearance, finger-like projections radiating outinto the cortex; this type is often found in the tail hairs of largermammals. Figures 1 and 2 are X300 photomicrographs of Brown Bear hair(both polarizer and analyzer have been rotated 45°).

Notice the moderately high birefringence using fully-crossedpolarizers (Figure 2). You can just begin to make out the scale patternalong the edge of the hair in the transmitted light photomicrograph (Figure1). The photomicrograph of the cross-section, Figure 3, shows a circular-to-ovalshape with a transparent medulla due to the stellate appearance. The medullaryindex was calculated to be 0.14.

Scale casts were made of the hairs using clear nailpolish in order to provide optimum study preparation of the scale pattern.The contrast and definition are both greatly improved (Figure 4); theirregular mosaic scale pattern is now easily visible. Images were capturedat X1200, 10 kV, using a scanning electron microscope (SEM), to show moretopographical detail which is visible at this higher magnification. Thissample is ~64 µm wide, and has 8-12 scales per 100 µm. The margins appearto be relatively smooth and near to one another (Figure 5).

Next, hair from Gorilla gorilla gorilla, otherwiseknown as the Western Lowland Gorilla was analyzed. Gorillas are greatapes, along with orangutans, chimpanzees, and bonobos.There are threesubgroups of gorilla: the Eastern Lowland Gorilla, the Mountain Gorilla,and the Western Lowland Gorilla. The Western Lowland Gorilla is slightlysmaller and lighter in color that the other two groups. Western LowlandGorillas have brownish-gray highlights among their black fur. The silverbackis the only fully adult male in a troop, and, as his name suggests, hepossesses a broad strip of silver fur across his back. They reside fartherwest in Africa than any other gorillas, and are currently on the endangeredspecies list. There is also a SSP on behalf of the Western Lowland Gorilla.

In Meltmount™ 1.662, notice the wide continuous medullain both transmitted light and fully-crossed polarizers; both images weretaken at X300 (Figure 6 & 7). With the polarizers crossed, the gorillahair shows relatively high birefringence (Figure 7).

The cross-section shows a circular shape with a medium-to-widemedulla. The sections that have a darker/black appearance indicate pigmentgranules. The medullary index was calculated to be 0.25 (Figure 8).

The scale cast of this sample shows a prominent,irregular wave pattern; the margins appear to be near, with rippled edges(Figure 9). The SEM image, taken at X500, 5 kV, shows this sample to be~120 µm wide and have 10-15 scales per 100 µm (Figure 10). Notice whatappears to be a damaged area towards the bottom of the image. This scratchedappearance may be due to all of the extensive grooming activity that gorillasundergo.

Lycaon pictus, otherwise known as the African WildDog, are medium-sized dogs that live on the savannah and open woodlandsof central and southern Africa. They have a very distinctively patternedfur coat, no two are exactly alike. Their colorful coats can range fromany combination of black, yellow, white, and dark brown. They possessa 12-16” long tail with a bushy white tip. The African Wild Dog is currentlyon the endangered species list and has a SSP working in its favor.

In Meltmount™ 1.662 you will notice a narrow, continuousmedulla, and a low birefringence when the polarizers are fully crossed.Both images were taken at X300 (Figure 11 & 12).

The cross-section shows a circular shape with a medium-to-widemedulla. Pigmentation is also present in these samples. The medullaryindex was calculated to be 0.47 (Figure 13).

A scale cast was made, and it shows an irregularmosaic pattern (Figure 14). The SEM image, taken at X900, 5 kV, showsthis sample to be ~ 70 µm in width, with 12-16 scales per 100 µm; themargins are near with smooth-crenate edges (Figure 15).

For a marine mammal species,we have Zalophus californianus. They, along with seals and walruses,belong to a “fin-footed” group called pinnipeds. They can be found anywherealong the Pacific coast of North America, from Vancouver, Canada to Baja, Mexico. They sometimes gather in large masses to hunt for fish, such as off thecoast of San Francisco where some consider them a nuisance. They are usuallybrownish-gray to silver in color with a thick coat of short fur and a heavylayer of fat under their skin to keep them warm in cold water. Their bodiesare smooth and streamlined which enables them to swim with little resistance.Once at very dangerously low populations, the California Sea Lion, and allother marine mammals, are now protected by the MMPA (Marine Mammal ProtectionAct) of 1972.

In Meltmount™ 1.662, noticethe unusual continuous globular medulla, with no visible scale pattern; incrossed polarized light there is low birefringence seen (Figure 16 & 17).

The cross-section shows the hair to be a cigar shape with a narrow medulla. Somepigmentation can be seen. The medullary index was calculated to be 0.32 (Figure18).

A scale cast was made to determine the scale pattern;the cast shows a distinct, irregular wave pattern, with margins that arenear with crenate edges (Figure 19). The SEM image, take at X600, 5 kV,was difficult to capture; the first attempt was unsuccessful because ofthe absence of a scale pattern. Finding this to be extremely unusual,a second attempt was made with the hairs turned over. The loss of thescale pattern on the exposed side of the hair (first attempt) is due,possibly, to streamlining in the water. The underside, or protected side(second attempt), revealed that there are 16-20 scales per 100 µm andthat this sample is ~150 µm in width (Figure 20). The angle at which thisimage was captured shows the loss of scales occurring toward the top ofthe image.

Not related to the Aardvark, Proteles cristatus, orthe Aardwolf, is actually a relative of the hyena family. Aardwolf isAfrikaans for “earth wolf.” The Aardwolf is found mainly in the open,sandy plains or bush country of eastern and southern Africa. Standinga mere 15-20” in height, the aardwolf possesses long loose under fur whichis mixed with larger coarser guard hairs. They have a defense mechanismwhich enables them to erect the hair of the mane to appear twice theirnormal size to defend against predators. Their body hair is usually yellow-graywith black stripes. Their legs are banded black with entirely-black paws.They have a bushy, black-tipped tail. The Aardwolf is not on the endangeredspecies list, but is classified as rare in South Africa due to human huntingand habitat destruction.

At X300 in Meltmount™ 1.662 you willnotice a very broad continuous medulla and moderately high birefringence using crossedpolarized light (Figure 21 & 22).

The cross-section shows the hairs to be oval-to-kidneyshape. The medulla appears to be wide; the medullary index was calculatedto be 0.62 (Figure 23).

The scale cast of this sample shows an irregularwave-mosaic pattern. The SEM image of this sample, taken at X400, 5 kV,shows the margins are near with crenate edges. The width of the sampleis ~163 µm, and there are 10-15 scales per 100 µm (Figure 24 & 25).

Among the observations of the animal hairs describedabove, morphological differences are apparent from species to species.It should be noted that the medulla may change within the length of thehair, and/or within different hairs on the body, as in the stellate appearancein the Brown Bear. The scale pattern may also differ, depending on environmentalconditions, as seen on the California Sea Lion hair, and possibly theWestern Lowland Gorilla hair.

Once again the cooperation of Brookfield Zoo, Brookfield,IL, in the collection of the animal hair samples used in this study isacknowledged and greatly appreciated. Thank you to Brian J. Bierman,McCrone Associates, for his assistance in capturing the SEM images.

Bisbing, R. E. (1982). The Forensic Identificationand Association of HumanHair.Forensic Science Handbook (Saferstein,R.; ed.). Prentice Hall, Englewood Cliffs.

Brunner, Hans, and Brian Coman (1974). TheIdentification of Mammalian Hair. Inkata Press, Melbourne.

Hicks, John W. (1977). Microscopy of Hair–A Practical Guide and Manual, FBI Laboratory Technical Supplement.Washington, D.C.

Moore, Tommy D., Liter E. Spencer, and CharlesE. Dugnoll, (1974). Identification Of the Dorsal Guard Hairs ofSome Mammals of Wyoming.Wyoming Game and Fish Department. Cheyenne,Wyoming.

Brookfield Zoo Web Site: http://www.brookfieldzoo.org.

P & G Beauty Science: http://www.pantene.com/haircare/hair_twh_12.htm.

Crime Library: http://www.crimelibrary.com

Hair Analysis: http://www.bergen.org

Phoenix Zoo: http://www.phoenixzoo.org

Brown Bear: http://www.bearbiology.com

Carnivora: http://www.press.jhu.edu