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Propositions for standardized measuring and description of lorises and pottos

Some general remarks concerning measuring, description and labelling

Measuring equipment recommended:
measurements down to 1 mm by direct reading with a ruler or with dividers, measurements down to 0.1 mm with vernier or dial calipers (Ansell, 1965).

Humane examination:
For wild animals, capture and handling for scientific examination is certainly a traumatic experience which may well endanger the animals´s health, cause stillbirths in pregnant females or increase the threat to fall victim to predators after release. Groves (2002 in press) recommends to anesthetize animals before measuring. For information about anesthesia in lorises see anesthesia chapter in the disease database; here, the short information may be sufficient that, while anesthesia suppresses sensory stimuli and tranquilizers at least calm down the animals, paralytic drugs (muscle relaxants) only paralyze tha animal. Ryder, 1978, after trying the effects of such drugs on himself; regards muscle-relaxing drugs paralyzing without diminishing consciousness as inhumane, causing terror and trauma in the animal.

Recommendation to measure both sides of an animal:
Lateral differences for instance of limb measurements have been found (B. Meier, pers. comm.; Seth 1969). In forms in which only few animals are available for examination, it might therefore be good to increase sample size by measuring both left and right limbs and other bilaterally occurring parts of the body in each animal (according to Swindler, 1976, in teeth there is no noticeable difference between right and left side; Schwartz and Beutel, 1995, however, recorded bilaterally different tooth measurements). In addition, comparison of individual size and asymmetry with the average values of the population may allow some conclusions concerning heterozygosity: in a diversity of species, relatively heterozygous individuals were found to have reduced fluctuating asymmetry and reduced morphological variation, suggesting a relationship beween heterozygosity and developmental stability. Individuals with extreme values for a morphological character whose variation is largely due to additive genetic variation will tend to be homozygous at the loci that influence the trait; they are also expected to be more asymmetric than those with central values. Relationship between extremity of measurements and asymmetry is highly dependant on how strongly variation of the morphological character in question is controlled by additive genetic variation and how many loci are involved. If the number of loci is large, then extremeness may provide a good estimate of genomic heterozygosity (Allendorf, Leary 1986).

See also information about asymmetry and variation within populations.
 

Comparability of measurements:
Comparability of measurements is usually limited by the following problems:

  1. Different measuring methods with different results; method often are not described together with given data.
  2. Results may vary with the personal working methods of observers, and
  3. Dead specimens may be fresh or relaxed in putrefecation, rigid with rigor mortis or slightly shrunken because of evaporation (Sumner 1927), making mesurements in general, but particularly measurements over joints inexact. Live animals probably struggle, in anesthetized animals regular seizure-like muscle contractions occur (B. Meier, pers. comm.). Such problems particularly limit the comparability of measurements over several joints.
Because of the existence of different procedures for obtaining a value, standardisation of measuring procedures, if possible, or at least reliable conversion / correction factors and clear information how each measurement was taken is necessary (see Ansell, 1965). In methods in doubt, use of several measuring procedures might be good as far as there is no reason to minimize the duration of handling, for instance of a terrified wildcaught animal.
 

Recommended accuracy:
in general to 1 mm; in very small mammals, an accuracy to 0.1 mm would be necessary for instance for hindfoot length, but usually such exactness cannot be achieved when different or unexperienced observers are involved (Ansell, 1965).

Necessary additional data concerning described animals / labelling of collected samples, according to Ansell (1965):

1) Dates ought to be unmistakeable (confusion of months and days impossible, include the century). The following dates ought to be noted:
date of death of the animal,
in case of captive care of wildcaught animals: in addition the date of capture / removal from natural habitat;
when necessary: date of preparation (for instance skin made up from an alcohol or formalin specimen).

2) Origin: locality traceable on maps: latitude and longitude; in addition place name (not only names of minor features unlikely to be on published maps)

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Loris and potto database in http://www.species.net
Draft for a measuring standard Last amendment: 9 May 2001
 

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