Relationship between hyponeophagia and adrenal cortex function in farmed foxes.

The adrenal cortex function of farmed blue (Alopex lagopus) and silver foxes (Vulpes vulpes) differing in their reaction in the feeding test were assessed. The urine cortisol:creatinine ratio was lower for those animals eating in the feeding test in comparison to those not eating in both species. In addition, eater silver foxes had lower baseline serum cortisol concentration and also lower serum cortisol concentration 2 h after ACTH administration than noneaters. There were no differences in any serum cortisol levels between the eater and noneater blue foxes. The weights of body and adrenals did not differ between confident and fearful animals in either species. The present study demonstrates that animals not eating in the feeding test may have higher fearfulness and be more stressed than animals eating.

Validation of the feeding test as an index of fear in farmed blue (Alopex lagopus) and silver foxes (Vulpes vulpes).

The reliability and validity of the eating behaviour in the presence of man (Feeding test) as an index of fear were assessed in farmed blue (Alopex lagopus) and silver foxes (Vulpes vulpes). Repeatability of the Feeding test was good in both species. No further habituation occurred after the fourth successive test in either species. In addition, the behaviour of both species was independent of the person who performed the test. The normal feeding interval, i.e., 24 h, between feed deliveries, was long enough to provide reliable results. The presence of a cage mate did not influence the blue foxes' response in the Feeding test. A significant relationship between the results of the Feeding test and the Tit-bit test in both species and between the Feeding test and fearfulness score in silver foxes indicate that all these tests measure similar features, most probably foxes' fear of humans. Those silver foxes that did not eat in the Feeding test had higher base levels of cortisol than the animals that did eat, providing further support for the above conclusion. The present study demonstrates that the Feeding test is a reliable, i.e., repeatable and free of random errors, and fairly valid fear test for blue and silver foxes. The Feeding test seems likely to give good results in measuring fear in farmed blue and silver foxes, but further investigations will be needed to fully validate it, especially for blue foxes.

Reproductive success of farmed blue foxes.

SUMMARY: The aim of this study was to provide basic data for the different components of reproductive performance of blue foxes under farm conditions. The foxes were mated naturally and the perinatal mortality of cubs was carefully recorded. This data allowed the evaluation of the effect of females' age and differences between years, and the maternal and paternal components of reproductive success. Generally the results were similar for all four years of the study. Altogether 2047 females (84.8 % of the total) gave birth to 22 941 cubs, of which 5.9% were stillborn and 11.4% died before weaning. Only in a very few cases (1.3%) was it the whole litter that was lost, and more commonly, there were some cub losses in almost one-half of the litters (46.9%). Abnormal birth and abortion of a part of a litter contributed most to reproductive failure of the vixen. Infanticide played a minimal role as a cause of postnatal cub mortality (0.3%). Death of the vixen was extremely rare. One half of all parturitions were dated between May 14 and May 28 and May 8 and May 20, for primiparous and multiparous vixens, respectively. Thus the parturitions peaked 5 days earlier (p < 0.001, median test) for multiparous vixens. The litter size was smaller and cub losses were higher for primiparous vixens than for multiparous ones. With a few exceptions, the age of the father or date of birth did not affect litter size or cub mortality. Postnatal cub mortality (y, %) decreased with age of the cub (x, days) and can be described by a simple equation: y = 15.3 - 11.2 log x, r(2) = 0.933. Fractional cub mortality increased with increasing litter size. Despite being significant, this increase was modest in extent. Low h(2) -values were observed for litter size at birth. ZUSAMMENFASSUNG: Der Zweck dieser Untersuchung war es, Basisinformation über verschiedene Komponenten der Reproduktion bei farmgezüchteten Blaufüchsen zu gewinnen. Die Fähen wurden naturlich gepaart. Eine besondere Aufmerksamkeit wurde der perinatalen Jungsterblichkeit gewidmet. Im allgemeinen waren die Ergebnisse für alle vier Jahre der Untersuchung gleich. Insgesamt 2 047 Fähen (84.8% von) warfen 22 941 Jungen. Von diesen wurden 5.6% totgeboren, und 11.4% starben später. Nur sehr selten war der ganze Wurf verloren (1.3%), aber Verluste fanden fast in der Hälfte der Würfe (46.9%) statt. Abnormale Geburt und Abort waren die häufigsten Ursachen der Geburtsprobleme der Fähen. Nur sehr selten brachte die Fähe ihre Jungen um (0.3%). Ebenso selten war ein Tod der Fähe. Eine Hälfte der Geburten fanden zwischen 14 und 28 Mai, bei Jungfähen und zwischen 8 und 20 Mai bei älteren statt. Die Jungfähen hatten kleinere Würfe und höhere Jungverluste als die Altfähen, wobei die Rüden fast keinen Einfluß hatten. Die postnatale Jungsterblichkeit (y, %) nahm mit Alter der Jungen (x, Tage) rasch ab, und kann mit einer einfachen Gleichung dargestellt werden: y = 15.3 - 11.2 log x, r(2) = 0.933. Jungsterblichkeit nahm mit der Grösse des Wurfes zu. Diese Wirkung war statistisch significant, zwar klein in Quantität. Die Heritabilitätswerte (h(2) ) der Wurfgrösse waren klein.