ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Wissenschaftliche Mitteilungen Niederösterreichisches Landesmuseum Jahr/Year: 2001 Band/Volume: 14 Autor(en)/Author(s): Ansorge Hermann, Suchentrunk Franz Artikel/Article: Aging polecats (Mustela putorius) and steppe polecats (Mustela eversmanni) by canine cementum layers and skull characters. (N.F. 436) 79-106 ©Amt der Niederösterreichischen Landesregierung,, download unter www.biologiezentrum.at Wiss. Mitt. Niederösterr. Landesmuseum 14 79-106 St. Polten 2001 Aging steppe polecats {Mustela eversmanni) and polecats (Mustela putorius) by canine cementum layers and skull characters HERMANN ANSORGE & FRANZ SUCHENTRUNK Keywords: Mustela eversmanni, Mustelaputorius, steppe polecat, polecat, aging, cementum annuii, skull Schlüsselwörter: Mustela putorius, Mustela eversmanni, Waldiltis, Steppeniltis, Altersbestimmung, Zahnzement-Jahresringe, Schädel Summary Based on skulls from Austria and eastern Germany, the possibilities of aging polecats and steppe polecats are considered and compared. Both species display discrete cementum annuii in thin sections of the upper canines. These annuii presumably result from annual growth breaks and are considered reliable age indi- cators. Particularly polecats from the eastern German study population that was subjected to a quite high hunting pressure showed a remarkable male-biased pro- portion of juveniles. A high concordance (92%) was found between age estimates by general skull morphology ("relative age classes") and true age as estimated by cementum annuii. Based on general age criteria of skulls, twelve qualitative (non- metric) skull characters were compared separately with the respective age in years as obtained from the annuii counts. Each of the twelve skull characters showed age-related changes. But no one allowed assessing age in years because of large overlaps of character states across age classes. Only five skull characters proved useful to reliably separate juveniles from older individuals, in a combined consi- deration. Most animals in their second year of life could be recognized by their respective skull characters. But precise aging of older animals was only possible by cementum annuii. There was a general concordance of age-related changes across skull characters. But some characters showed sex-specific differences in changes with age. This fact has to be considered in either species when carrying out age estimates based on skull morphology. ©Amt der Niederösterreichischen Landesregierung,, download unter www.biologiezentrum.at 80 HERMANN ANSORGE & FRANZ SUCHENTRUNK Zusammenfassung Anhand von Schädelmaterial aus Österreich und Ostdeutschland werden Mög- lichkeiten der Altersermittlung für den Steppen- und den Waldiltis erarbeitet und verglichen. Beide Arten zeigen im Zahnzement von Dünnschnitten der oberen Canini gut erkennbare Wachstumsunterbrechungen, die Jahreslinien darstellen. Das so ermittelte Alter wird als korrekte Bezugsgröße angenommen. Die Altersstruktur ist besonders bei den Waldiltissen Ostdeutschlands, die einem höheren Jagddruck ausgesetzt waren, stark in den jüngeren Bereich gestaucht und auffällig zugunsten der Männchen verschoben. Eine Schätzung in „relative Altersklassen" nach allge- meinen Schädelmerkmalen ergibt eine recht hohe Übereinstimmung mit den Er- gebnissen der Zahnschnitte (92%). Zwölf Schädelmerkmale werden einzeln nach ihrer Ausprägung numerisch bewertet. Sie weisen zwar alle eine altersabhängige Entwicklung auf, erlauben aber wegen der großen Überlappungsbereiche nicht eine eindeutige Zuordnung in Altersklassen. Nur fünf Merkmale sind bei gemeinsamer Betrachtung geeignet, um Jungtiere sicher von älteren zu unterscheiden. Die mei- sten der Tiere im zweiten Lebensjahr können aber auch noch gut ihrer Altersklasse zugeordnet werden. Für eine weitere Altersaufteilung älterer Tiere müssen die Jah- reslinien im Zahnzement herangezogen werden. Die Möglichkeiten der Alterser- mittlung anhand der Schädelmerkmale von Waldiltis und Steppeniltis stimmen grundsätzlich überein. Zwischen den Geschlechtern bestehen in wenigen altersab- hängigen Merkmalen aber sichere Unterschiede, dies ist bei einer Altersschätzung zu berücksichtigen. 1. Introduction The correct age determination of dead specimens is a prerequisite for studies on diverse aspects of the biology of mammal species. Information on the age of individuals is not only essential for constructing models of population structure, life expectancy, mortality rates etc. (see e.g. CAUGHLEY 1980). Reliable age estima- tes of individuals are necessary for diverse ecological and evolutionary studies, such as testing hypothesis of variation of body size and weight. Furthermore, age estimates are essential for evaluating the meaning of ontogenetic and static allo- metry in systematic comparisons, to interprete changes in diverse physiological parameters, to understand characteristics of the reproduction biology, pathological developments or findings of intoxication or contamination (see e.g. REMPE 1970, KRÜGER 1996, KRUUK et al 1997, POWELL & KING 1997, PERTOLDI et al 1998, KRUS- KA & SCHREIBER 1999). Often a more detailed age classification of specimens is desired than merely a separation into juvenile and adult categories. Diverse me- thods have been developed to estimate the real age of dead individuals as precise as possible (see e.g. MORRIS 1972). ©Amt der Niederösterreichischen Landesregierung,, download unter www.biologiezentrum.at Aging polecats and steppe polecats 81 For polecats (Mustela putorius L., 1758), various schemes of age estimation have been based on the development of diverse skull characteristics (HABERMEHL & RÖTTCHER 1967, REMPE 1970, BUCHALCZYK & RUPRECHT 1977, STUBBE 1989). However, an accurate assessment of a polecat's age can only be achieved by coun- ting the annual growth lines in bones or teeth (KLEVEZAL & KJLEINENBERG 1967, GRUE & JENSEN 1974, FANCY 1980, KLEVEZAL 1988, 1996). In polecats, KLEVEZAL & KLEINENBERG (1967) described periostal lines in the lower jaw, and GRUE & JEN- SEN (1974) found incremental cementum lines, that were considered to reflect the real age of the animals (see also table 10 in KLEVEZAL 1996). Such growth lines (annuii) of polecats have been studied in population ecological contexts by WEBER (1987) and ANSORGE (1994). As to our knowledge no comparison of aging polecats by skull characteristics and tooth annuii has been untertaken so far. In steppe polecats (Mustela eversmanni Lesson, 1827), characteristics of skull development were used to separate juveniles and adults (HEPTNER & NAUMOV 1974, WOLSAN 1993a); annual layers in mandibles were mentioned only in the context of aging individuals from Kasachstan (GVOZDEV & STRAUTMAN 1982). Here, we report for the first time on age determination of steppe polecats based on cementum annuii counts in tooth sections. In addition, in order to check the reliability of morphological criteria of skulls for aging steppe polecats and polecats, we compare age estimates as derived from various skull characteristics with the respective cementum annuii counts in the same individuals. 2. Material and methods 2.1 Specimens studied We studied 51 skulls of steppe polecats and 249 skulls of polecats. Most of the individuals were trapped or shot by hunters. Only few were collected as road-kills. All steppe polecats were from eastern Austria (provinces of Lower Austria and Burgenland), mainly killed after 1990. Among the polecats, 194 individuals were from Upper Lusatia in the southeast of eastern Germany; all were collected after 1980. Twenty-seven polecats were from eastern Austria (provinces of Lower Au- stria and Burgenland), largely from the overlap zone of both species; another eigh- teen were from southern or central Austria (provinces of Styria and Carinthia), and ten from northwestern Austria (Upper Austria). The bulk of the Austrian polecats was collected in various years of the 20th century; only few individuals were col- lected by the end of the 19th century. While most steppe polecats were collected during late summer, polecats were collected almost exclusively between autumn and spring. The Austrian skulls are either in the mammal collection of the Natural ©Amt der Niederösterreichischen Landesregierung,, download unter www.biologiezentrum.at 82 HERMANN ANSORGE & FRANZ SUCHENTRUNK History Museum Vienna (NMW) or in the study collection of the Institute of Wild- life Ecology at the Veterinary Medicine University of Vienna. The skulls from Upper Lusatia are from the mammal collection of the State Museum for Natural Sciences Görlitz (MNG). Species diagnoses were read from specimens lables and acknowledged by the authors or based on skin and skull characters (see HEPTNER & NAUMOV 1974, WOL- SAN 1993b) in case of the recently collected specimens that were dissected by the authors. 2.2 Aging methods Each specimen was aged independently by counts of cementum annuii and skull characteristics. 2.2.1 Tooth sections and annuii counts All skulls were aged according to cementum annuii counts (e.g., GRUE & JEN- SEN 1974, KLEVEZAL 1996). Longitudinal sections (50 - 100 |im ) of upper canine roots were produced with a low-speed precision saw (Isomet - Buehler) and annuii (i.e., narrow dense lines) were counted in unstained sections under reflected light (lateral illumination) with a dissecting microscope (DRISCOLL, JONES & NICHY 1985, ANSORGE 1995). All annuii counts were made by one author