11

1 2 3 4 5 6 7 8 9 10 11 12 13 14

the microscopic examination on the cellular level of all relevant organs/tissues (=histological investigation): External examination • Scanning for and documenting any individual marking of the carcass (collar, microchips, rings in birds) • Body condition, skin, pelage/plumage, body orifices, signs of injuries/predation Internal examination of organs and body cavities • Inspection of internal body cavities • Dissection and assessment of inner organs: Size, weight, shape, colour, texture… Sampling for additional investigations Histological Examination • Rule out/confirm disease 52 • Ageing of tissue damage (e.g. wounds) and inflammations (acute, subacute, chronic, etc.) • Exact analysis of swellings (tumour, old trauma, etc.) • Specific histopathological findings (e.g. lead intoxication) 6.1.2 Some considerations for on-site necropsies In certain situations, an on-site necropsy may be deemed necessary. These circumstances include: • Size of the animal • Terrain making transport of carcass difficult • Environmental conditions • Time of year • State of the carcass • Available personnel However, every effort should be made to transport the carcass to a pathological facility that act as the first responding lab. On-site necropsies can be very challenging and chances are high that important evidence is lost, e.g. due to lack of radiography in the field, contamination of samples due to unhygienic environment, lack of proper sampling tools/containers and many more. 6.1.3 Special questions during necropsy in wildlife forensic cases 6.1.3.1 Species determination While the determination of distinct species is straightforward in (large) mammals like wolf, bear and lynx, the correct species-identification of birds of prey by morphological characteristics (size, coloration of plumage etc.) can be challenging. This is especially true for young individuals aged three years or less in certain species, e.g. harriers. Although there are many field guides available for easy identification of birds and other animals, the examiner may refer to biologists, especially ornithologists, if in doubt. If no working relation has yet 53 been established with these experts, any museum of natural history or the biology department of a university may assist in finding one. If no correct species determination is possible by morphological characteristics, e.g. the carcass being highly decomposed, a genetic investigation of any tissue of the carcass will provide the respective information. For sampling details and further information on genetic investigations, see the particular chapter in this book. 6.1.3.2 Age Determination In a few cases, the correct determination of the age of an individual victim may be straightforward if the individual “is known”. This may be the case if the individual was released in course of a reintroduction program or if it had been captured and marked (radio collar, microchip, ringing in birds etc.) during a scientific study. Normally, the age of the individual is determined in course of these projects/studies and thus contacting the respective project leaders is helpful. In all other cases, age determination can be complex and advice from (zoological) specialists may be sought. As with species identification, various morphological characteristics are used depending on species: Size and weight of the individual; coloration of pelage/plumage; ossification of various bones and bone sutures (e.g. skull); ossification of various chondral tissues; dimension of bony structures; dentition, eruption and wear of teeth (in mammals). In large carnivores, the dental characteristics, especially of the incisors, show consistent alterations with age and thus allow assigning an individual at least to distinct age categories, in lynx e.g. < 1 year, 1–2 years, 3–6 years, 7–9 years, 10–13 years, ≥ 14 years. Very exact results of age determination in wolves, bear and lynx may be obtained by microscopic analysis of the so-called cementum annuli rings of the incisors, canines or premolar teeth (annually formed rings in the cementum layer of these teeth), but this technique is performed only by few specialised laboratories. With the exception of some species of birds of prey (e.g. harriers), whose plumage show distinct coloration up to an age of approximately three years, age determination in birds is often restricted to simply classifying them as juvenile or adult since no distinct morphological 54 characteristics allow for a more exact age classification. Remember that genetic analysis will not aid in age determination. 6.1.3.3 Determination of Post-mortem Interval Right after death, many simultaneous chemical and physical processes commence in a carcass, leading to decomposition and, in most cases if undisturbed, final skeletisation. Decomposition comprises the autolysis process (decay of carcass by own body enzymes) and, sometimes, the putrification process (decay by bacteria). Under certain circumstances (dry climate with low humidity) mummification, literally the drying of the carcass, may occur. Based on the sequence of processes, the pathologist may be able to determine at least a rough estimate of the time elapsed since the death of the individual during necropsy. Features that occur after death include: − livor mortis: settling of blood in a carcass in a gravity dependant pattern − rigor mortis: rigidity and subsequent relaxation of muscles after death − algor mortis: cooling of body after death − discoloration: (greenish) colour due to degradation of haemoglobin − bloating: abdominal swelling due to (bacterial) gas discharge, mainly in herbivores − sloughing of skin/hairs − later stages of decay It must be noted however, that all these processes are highly variable depending on many intrinsic and extrinsic variables, including species and size of animal, ante-mortem activity, cause of death (possible diseases, poisons leading to convulsions, e.g. carbofuran), environmental conditions (especially ambient temperature and -moisture, exposure to sun and rain) and many others. In large mammals, e.g. a bear in winter fur and with large fat depots, cooling is considerably slower than in emaciated birds. In human forensic sciences, postmortem cooling models (e.g. Henßge’s nomogram) have been