Techniques for the Study of Primate Population Ecology (1981) / Chapter Skim
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TECHNIQUES FOR SEXING AND AGING PRIMATES
TECHNIQUES FOR SEXING AND AGING PRIMATES
Pages 81-127
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From page 81... ...
If we wish to ascertain whether a species has a monogamous or polygamous social organization, distinctions between adults and nonadults and between adult males and adult females will suffice. But if we seek to understand the dynamics of population growth and patterns of mortality and natality, as in life-history analyses, knowledge of the age and sex of all individuals in a large population sample is indispensable.
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From page 82... ...
A survey of morphological traits that are useful for aging, sexing, and identifying individuals belonging to all species of primates is beyond the scope of this chapter. Indeed, establishing a key for aging wild primates is impossible because accurate age data for most species under natural conditions are lacking.
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From page 83... ...
Although size differences by sex in adults generally favor the male, the importance of assigning sex on the basis of genitalia rather than on size alone is underscored by the fact that the adult female may be slightly larger than the adult male in marmosets, Callitrichidae, and the black gibbon, Hylobates concolor (Rails, 1976)
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From page 84... ...
The difference is most marked in adults. ESTIMATING RELATIVE AGE CLASSES FOR CENSUSES Because of the limited time available during broad surveys and many transect censuses, investigators have used the size-scaling methods of early primate field studies to develop general age classifications and have assigned estimated chronological ages to these size classes on the basis of information from known-aged captive animals.
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From page 85... ...
Usually they are larger than those of adult females. As a practical starting point, adult females have given birth to at least one infant and often may be
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From page 86... ...
SUB ADULT MALES Subadult males are separately identified among sexually dimorphic species in which the adult males are larger than the adult females. They are intermediate in size between large juvenile males (or adult females)
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From page 87... ...
Several juveniles of varying sizes and ages usually occur in any social group. It has been common in field studies to recognize several classes with each class encompassing a range of sizes that is distinct from other such classes.
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From page 88... ...
DIRECT MEASUREMENT OF CHRONOLOGICAL AGE The most accurate measurement of age is direct, and the most convenient unit for measuring age is the year. The year is also a biologically meaningful unit of measurement for age because primates in most habitats are subject to seasonal environmental changes that directly influence seasonal variations in their food TABLE 5-1 Physical Characteristics of Amboseli Baboons Class Physical Characteristics Estimates of Ages (years)
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From page 89... ...
Subadult male Development of secondary 4-6 6-8 sexual characters: mantle, long canine teeth, large size, greater musculature than females. Scrotum (testes)
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From page 90... ...
INDIRECT MEASUREMENT OF CHRONOLOGICAL AGE Estimating chronological age from established morphological criteria is a compromise between relative and direct measurements of age and serves to establish chronological ages between and within relative age classes. Several changes take place in various parts, of the body as individuals grow.
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From page 91... ...
Weights can be read, with the aid of binoculars, from several meters away. ESTIMATING CHRONOLOGICAL AGES OF INFANTS In species in which changes from a natal pelage and skin color to an adult type occur, these changes can be used to age infants.
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From page 92... ...
Month 9-12 Pinnae are fully or almost fully pigmented black. In the toque macaque, changes in the texture and color of the natal coat are variable between 2 and 5 mo of age and therefore are not very useful for aging within this age range.
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From page 93... ...
ESTIMATING CHRONOLOGICAL AGES OF JUVENILES The problem of aging juveniles is to assign chronological ages to a gradient of body sizes between 1-yr-old infants and adult females. Age estimates are aided if we know the duration of the juvenile phase (or the age at which it ends)
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From page 94... ...
If critical weight needs to be attained in order to reproduce, then any factor that may affect the rate of growth, such as food supply or social behavior, should influence the age at onset of reproduction or the duration of the juvenile phase. For example,
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From page 95... ...
However, long-term field data for the slightly smaller toque macaque have shown that wild females of this closely related species do not experience their first birth until they are 5.5-6.5 yr old (Dittus, 1975, and unpublished data)
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From page 96... ...
96 at |3 i a 3 nt u i/i .§ & U .2?
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From page 97... ...
Wild toque macaques, Macaca sinica, living in good habitats weigh more than those living in marginal habitats, and socially high-ranking animals, which enjoy priority of access to resources, grow faster than low-ranking ones (W.
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From page 98... ...
Assigning ages to size classes is justified, however, where discontinuities in size distribution are apparent and are the result of a birth pulse. A well-defined birth season is one in which births in a population are fairly well synchronized, so that most individuals of a given birth season are fairly close in body size and may be recognized as belonging to a distinct age class or cohort.
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From page 99... ...
Sex as a Factor in Growth Differences Infant and juvenile males grow faster than their female peers among several primates studied in captivity -- for example, rhesus
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From page 100... ...
If growth rates by sex under natural conditions are unknown, an attempt to adjust age classifications on the basis of sex differences in growth may assume a degree of accuracy in age determination that under field conditions is unjustified. Among infants and young juveniles especially, growth differences by sex are slight, and the task of making accurate estimates is made more difficult by size differences resulting from differences in date of birth relative to peers of the same birth season or cohort.
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From page 101... ...
ESTIMATING CHRONOLOGICAL AGES OF SUBADULT MALES The criteria defining the upper limit of the juvenile male phase also define the lower limit of the subadult male phase. Examples of morphological changes in males of known ages are provided from the two primates for which such data are available from wild populations.
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From page 102... ...
. Although toque macaques may be exceptionally well suited for the identification of age-specific characters, adults were assigned ages only after the investigator had accumulated 3 yr of field contact with the macaques.
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From page 103... ...
The pale or slightly flushed complexion of young adult females may be intensified by middle age or old age to bright red and may deepen to bluish red in very old age. However, some young adult females also have bright red faces (but more even)
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From page 105... ...
S O fN ,s s §1 55 b O b 0 b b b b b c o B 3 O* 3 O1 1 6 Hamadryas baboo Chacma baboon 3 Japanese macaque Rhesus macaque Pigtailed macaque Toque macaque Stumptailed maca Grey langur White-handed gib c & § u M £ Si ,*
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From page 106... ...
The canines of adult male toque macaques in their prime (judged to 10-15 yr old) are fully erupted, sharply pointed, and clean ivory colored.
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From page 107... ...
The most useful characters for assessing ages intermediate between young adult and very old adult are those that change gradually and progres FIGURE 5-5 An adult male toque macaque, "Harris." Left, in December 1971 when middle-aged; right, in April 1975 after he had acquired a new cut on his upper lip. The red spot under the left eye has grown larger, and several new small red spots have appeared.
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From page 109... ...
SP . i •il c > i ^ 1 M Si n .S 3 ^1 X X X ^ "a Q " Sifaka Propithecus verreauxi (Jc 'White-fronted capuchin Cebus c Toque macaque Macaco sinica t d Rhesus macaque Macaco mulat "Gelada baboon Theropithecus g ^Chacma baboon Papio ursinus ( *
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From page 110... ...
are divided equally among the remaining four adult age classes for each sex, each class thus spanning 5 yr. IDENTIFYING INDIVIDUAL PRIMATES BY NATURAL MARKINGS Free-living primates can be identified individually if they possess recognizable natural or artificial markings that distinguish them from other individuals.
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From page 111... ...
and those that change rapidly with maturation (e.g., color of pelage or skin among infants or the body size of subadult males)
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From page 112... ...
The distribution of the color varies. The facial skin color of adult males and of juveniles of either sex may be pale, typical medium tones, beige, slightly flushed, or grayish.
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From page 113... ...
These relate to the size, color, configuration, and distribution of spots or scars. In the toque macaque, such spots occur mainly on the face.
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From page 114... ...
__ Notches Troop: B Harris Dec. 15, 1971 Adult male: middle aged Pelage: mid-brown, tinted slightly orange Toque: round overtoque strands project beyond sides of head; pretoque small and V-shaped Face color: flesh color, lip pigment slight dip Ears: both cut; left tragus black, right blotched Ventrum: no white patches; all even light blue FIGURE 5-6 Sample identification cards (3" X 5")
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From page 115... ...
As in the toque macaque, individual differences register best in the pelage color, configuration of the head hair, and in pigment patterns of the exposed skin. Gray langurs have darkly pigmented facial and body skin.
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From page 116... ...
In tall closed-canopy forests the observation of primates is more limited, but investigators working in such habitats have found there a range of natural markings for recognizing individuals. In some cases it has not been possible to identify individual markings for all ages, and investigators have used marker individuals, location, and group affiliation to identify inage sex 1 any age m/f m/f 1/J m/f J m/f J/SA A f A m FIGURE 5-7 Forehead patterns of Cebus capucinus.
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From page 117... ...
reported in identifying individual red colobus, Colobus badius, in Uganda are typical of those that have been faced by field workers in observing shy canopy primates. He reported: Among the red colobus, adult males were most easily distinguished as individuals.
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From page 118... ...
118 TECHNIQUES IN PRIMATE POPULATION ECOLOGY ritory, it is important that a decoy be adequately protected. When used in a trap, decoys should be double-caged so they cannot be bitten.
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From page 119... ...
Techniques for Sexing and Aging Primates 119 Once the animals are in the trap the job is to get them out without traumatizing them or the investigator. It may be possible to chase small primates out of the trap into a cloth or string bag, but it is desirable to anesthetize larger primates before removing them from the trap.
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From page 120... ...
120 TECHNIQUES IN PRIMATE POPULATION ECOLOGY Germany. Zoo veterinarians frequently have need of such equipment and may be able to advise you about its use.)
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From page 121... ...
If the animals do not need to be identified individually at a distance, they may be marked with ear notches, with ear tags, or with tattoos. If the animals do need to be identified at a distance, they may be marked by clipping and dyeing hair, using collars and freeze branding.
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From page 122... ...
Under some circumstances these notches will be distinguishable at a distance. The only problem with ear notches is that animals sometimes notch their own ears or their neighbors' in fights.
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From page 123... ...
Collars can also be made of ball chain. They can be cut to size easily,
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From page 124... ...
Freeze branding does not hurt at the time it is done, but it does
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From page 125... ...
. To make tooth casts one needs plastic to make dental trays of the right size and shape, alginate for obtaining the molds, and dental stone to make the casts.
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From page 126... ...
The dental stone will displace or mix with the water deep in the cusps, whereas it will not mix with air bubbles that get trapped in the cusps in the mold. Be sure to build up a good thickness of dental stone above the teeth, for this will be the base of the cast when you turn it out.
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From page 127... ...
Note the animal number and the date so that you will not confuse the cast with any you may make later of the same animal, if you recapture it. New dental materials for tooth casts are becoming available.
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