Silver Fox Research Articles

Comparative studies on testis, epididymis and serum hormone concentrations in foxes, and hybrids during the pre-breeding period

Silver fox and blue fox belong to different genera, and the hybrid males are reproductively sterile. In the present study, there was a comparison of testicular and epididymal morphology and serum hormone concentrations among silver foxes, blue foxes, and the hybrids during the pre-breeding period, using 20 male silver foxes, 20 male blue foxes, 15 male HSBs (silver fox male × blue fox female hybrids) and 15 male HBSs (blue fox male × silver fox female hybrids), respectively. Hybrids had a smaller diameter of seminiferous tubules than pure-species males, and testes of hybrid males did not differ in mean size and relative weight from pure-species males. There were many Sertoli cells and spermatogenic cells in silver foxes and blue foxes, while numbers of spermatogonia and primary spermatocytes were less with no secondary spermatocytes in the hybrids. Furthermore, mean serum testosterone and estradiol concentrations in the hybrids were less, and FSH, LH, and PRL were greater than that in silver foxes and blue foxes (P < 0.05), suggesting that lesser concentrations of testosterone and estradiol and greater concentrations of FSH, LH and prolactin can inhibit the completion of spermatogenesis during the pre-breeding period. The results indicate that fox hybrid sterility may result from failures at the early stages of spermatogenesis.

Age-Related Changes in the Tissue Antioxidant System of Canids

The study was aimed at determining tissue antioxidant levels in three closely related albeit ecologically different Canidae species: the raccoon dog (Nyctereutes procyonoides), silver fox (Vulpes vulpes) and blue fox (Vulpes lagopus), aged 0.5 (juvenile), 1.5–3.5 (adult) and 4.5–5.5 (aging) years. Some tested parameters were found to be species-specific: as compared to other species, raccoon dogs and blue foxes exhibited higher α-tocopherol levels in the liver and kidney, blue foxes were characterized by a higher activity of the antioxidant enzymes in the kidneys, while silver foxes had higher glutathione (GSH) levels in the liver, kidneys and heart. The antioxidant defense system in all organs of the tested species was distinguished by a relative stability. In raccoon dogs, the retinol level in the heart increased with age, while in silver foxes it is only superoxide dismutase (SOD) activity in the kidneys and the GSH level in the liver and heart that underwent significant changes with age. In blue foxes, aging was accompanied by an increase in liver retinol and kidney α-tocopherol levels as well as a decrease in the kidney GSH level. Besides, sex differences were found in antioxidant levels in blue foxes. Our results are consistent with the data obtained by other authors for other animal species, indicating a mixed pattern of age-related changes in the antioxidant defense system of carnivorous canids. While some antioxidants rise and the other fall, the functionality of the whole system does not appear to be disturbed. Ecological and physiological features of different mammalian species may determine the adaptive potential of animals and affect the tested indicators of the antioxidant defense system during late postnatal ontogenesis.

Evaluation of chromosomal instability in somatic cells of farmed foxes.

The micronucleus (MN) test is a common tool used to evaluate cellular genetic instability at the chromosomal level. It determines the effect of physical, chemical and environmental factors on DNA, and thus the body's individual resistance to harmful substances. The karyotypes of blue and silver foxes and their interspecific hybrids are characterized by morphological and structural variation. This variation is partly attributable to the presence of chromosomal polymorphism, which may significantly influence the stability of genetic material in the cells of these species. The objective of the study was to evaluate genetic material stability in selected Canidae species. To this end, analyses using the MN test were performed. Binucleated cells (BNCs) were analysed in microscopic preparations, and the number of micronuclei was determined within these cells. For the proportions of both MN and BNCs, highly significant differences were observed between the fox species. The interspecific hybrids differed from the other fox species in MN percentage. The lowest average was noted in blue foxes (3.33) and the highest in interspecific hybrids (15.21).

Genomic responses to selection for tame/aggressive behaviors in the silver fox (Vulpes vulpes)

Animal domestication efforts have led to a shared spectrum of striking behavioral and morphological changes. To recapitulate this process, silver foxes have been selectively bred for tame and aggressive behaviors for more than 50 generations at the Institute for Cytology and Genetics in Novosibirsk, Russia. To understand the genetic basis and molecular mechanisms underlying the phenotypic changes, we profiled gene expression levels and coding SNP allele frequencies in two brain tissue specimens from 12 aggressive foxes and 12 tame foxes. Expression analysis revealed 146 genes in the prefrontal cortex and 33 genes in the basal forebrain that were differentially expressed, with a 5% false discovery rate (FDR). These candidates include genes in key pathways known to be critical to neurologic processing, including the serotonin and glutamate receptor pathways. In addition, 295 of the 31,000 exonic SNPs show significant allele frequency differences between the tame and aggressive populations (1% FDR), including genes with a role in neural crest cell fate determination.

Cell cycle progression and different ways of cell and genome reproduction in the invasive trophoblast cells of the silver fox placenta

Relationship between cell cycle progression and different ways of cell and genome reproduction (regular mitotic cycle, polyploidizing mitoses, endoreduplication, depolyploidization) has been studie...

Dr. E. A. (Al) Corley (1931–2017)

Al Corley was a dedicated veterinarian, radiologist, and academician who spent his 60 year career teaching, guiding, and mentoring veterinary students, residents, and animal owners. Al was born in South Carolina in 1931 and as a young man enjoyed working with animals and was first exposed to veterinary medicine while in high school when he worked in a small animal clinic. After graduating from Clemson University, he served 2 years in the U.S. Army achieving the rank of 1st Lieutenant and was stationed in Korea. He was awarded the Bronze Star and Purple Heart Medals. He entered veterinary school at the University of Georgia and received his Doctor of Veterinary Medicines in 1957. Dr. Corley was on the Georgia faculty for 7 years and then pursued additional training at Colorado State University where be obtained a PhD in radiology in 1966 under W.D. Carlson. He then accepted a faculty position at the University of Missouri - College of Veterinary Medicine and helped develop the department of radiology. He became Full Professor and served as Associate Dean. During his tenure at Missouri, he received many honors and awards for teaching and leadership. He became a Diplomat of the American College of Veterinary Radiology in 1966 and he served on Executive Council and was American College of Veterinary Radiology President from 1969 to 1970. Dr. Corley was affiliated with the Orthopedic Foundation for Animals beginning in 1967. In 1981, he was named Director and later became President of the Orthopedic Foundation for Animals. He authored many scientific publications and was a popular speaker to veterinarians and breeders about genetically transmitted diseases monitored and tabulated by the Orthopedic Foundation for Animals. In 1996, he retired from the Orthopedic Foundation for Animals, but continued to consult until 2017. Al was universally admired by his students, faculty, and residents. Nicknamed “The Silver Fox,” his manner, speech, and actions contributed to his southern gentleman persona. He was well organized, had a wonderful sense of humor, and encouraged his students and residents to do their best and helped many advance their careers. He enjoyed time with family and as an avid Mizzou fan, he looked forward to the start of football and basketball, always hoping for a better season. Al loved to travel and did so until his health failed. He is survived by his loving wife, Meredith, a brother, two sons, a stepson, a stepdaughter, 10 grandchildren, and 11 great-grandchildren. Al will be missed by many and will always be remembered as an exceptional veterinarian, family man, and human being.

Hippocampal glucocorticoid receptor and microRNA gene expression and serum cortisol concentration in foxes selected for behavior toward humans

In many cases, stress reactivity is one of the important bases of aggressive behavior. It appears as if reduced stress reactivity underlies an abrupt decrease in aggression towards man in domesticated animals. However, the mechanisms of this reduction have yet to be resolved. In this work, we used an experimental domestication model, the silver fox selected for many years for the response to humans to study cortisol stress reactivity in tame and aggressive foxes in response to immobilization in human arms. Additionally, these behavioral fox groups were explored for one of the important mechanisms of glucocorticoid negative feedback, the expression of the glucocorticoid receptor gene (NR3C1) in a portion of the dorsal hippocampus. In recent years, attention has been paid to differences in miRNA expression patterns between animals with different behavior and stress reactivity, as well as to miRNA regulation under stress. The same applies to NR3C1 mRNA as well. That is why we performed a miRNA-seq analysis on a portion of the fox dorsal hippocampus. It has been demonstrated that immobilization in human arms leads to significantly higher stressinduced cortisol levels in aggressive than tame foxes. At the same time, no differences have been found between hippocampal NR3C1 gene expression and the pattern of miRNA expression. Thus, reduced stress reactivity in foxes during selection for the absence of aggressive responses and for the presence of emotionally positive responses to humans does not seem to be associated with important mechanisms of regulation such as alterations in hippocampal NR3C1 gene expression or microRNA-mediated silencing.

Multiple-strainTrichophyton mentagrophytesinfection in a silver fox (Vulpes vulpes) from a breeding farm

Dermatophyte infections are extremely frequent worldwide, and their epidemiological features and distribution make them one of the most frequent infections all over the world. We identified and analysed multiform T. mentagrophytes strains isolated from a silver fox (Vulpes vulpes) kept on a breeding farm. Identification of dermatophyte strains was carried out traditionally by correlating both the clinical manifestations of the infection with a micro- and macroscopic examination. To confirm the species affiliation fully, molecular differentiation methods were used. DNA was isolated from the dermatophytes with the phenol-chloroform method. The reaction of chitin synthase 1 (chs1) amplification was carried out to confirm the dermatophytes. The phylogenetic analysis was based on the ITS sequences. The polymerase chain reaction melting profile (PCR-MP) procedure was used for differentiation of dermatophyte genomes. Direct analysis of the material sampled from the clinical lesions revealed the presence of arthrospores in the samples collected from all animals with skin lesions. The macromorphology of the colonies obtained from material sampled from the same individual was not homogeneous. The PCR-MP electrophoregram indicated high variability of their genomes. Although the dermatophytes were isolated from one infected fox, no two identical genomic profiles were obtained. The PCR-MP result corresponds with the phenotypic diversity of the isolates. The findings about the multiple dermatophyte infection in one individual complicate any future epidemiology work and other clinical investigation. Previously, using only morphological characteristics, it had been assumed that one fungal isolate per patient could be diagnosed. The novel findings encourage application of the newly developed molecular typing methods in the diagnosis of dermatophytosis.

Serum Concentration of Macro-, Micro-, and Trace Elements in Silver Fox (Vulpes vulpes) and Their Interrelationships with Morphometric, Densitometric, and Mechanical Properties of the Mandible.

The optimal content of macro-, micro-, and trace elements in tissues ensures proper systemic growth and development and optimal health status in animals and humans. However, very little is known on the elemental content in the plasma compartment in Silver fox. The aim of this study was to determine the content of selected elements in serum obtained from 8-month-old female (N = 8) and male (N = 7) silver foxes. Moreover, relationships of the evaluated elements with the morphological, densitometric, and mechanical parameters of the mandible were determined. Serum content of 12 different elements was measured using inductively coupled plasma-atomic emission spectrometry. The morphometric and densitometric properties of the mandible were determined using quantitative computed tomography method, while mechanical endurance was tested using a three-point bending test. Serum concentration of calcium was significantly higher by 20% in male foxes (P = 0.01), while manganese concentration was significantly lower in males by over 17% (P = 0.03). Positive correlations of serum concentration of calcium, phosphorus, and magnesium with the morphological traits of the mandible such as weight, length, and bone volume were stated (P < 0.05). In the group of elements playing regulatory functions, the positive relationships between serum concentrations of selenium, chromium, manganese, copper, and cobalt were found (P < 0.05). The elaborated experimental model may serve for further studies on foxes, especially focused on nutritional factors affecting elemental homeostasis, whole-body metabolism, and systemic growth and development. Daily diet formulation and precise delivery for farm foxes, together with relatively large animal population maintained at the same environmental conditions, regularly subjected to slaughter procedure, enable economical experimentation with various dietary and pharmacological manipulations.

Evaluation of BrdU Influence on Sister Chromatid Exchange in Arctic and Silver Fox

Evaluation of BrdU Influence on Sister Chromatid Exchange in Arctic and Silver Fox

Faecal cortisol metabolites as an indicator of adrenocortical activity in farmed silver foxes (Vulpes vulpes)

Measuring glucocorticoid metabolites in faeces has proven a useful, non-invasive method to monitor adrenocortical activity in several farm and wild species. Unlike plasma cortisol, whose sampling requires restraint and blood draws, faecal cortisol metabolites (FCM) may be particularly suitable for farmed silver foxes as these animals are sensitive to handling by humans. Prior to using FCM as a potential indicator of stress in silver foxes, however, a proper physiological and/or biological validation is required. Here, we determined FCM concentrations in 30 silver foxes (10 adult vixens, 10 juvenile females and 10 juvenile males) every alternate hour for 24h after 1) an increase in cortisol induced by injection with synthetic ACTH (hereafter ACTH), and 2) a 2min period of handling and restraint. Baseline FCM values, recorded every fourth hour for 24h before the ACTH and handling treatments, served as controls. FCM values increased significantly following ACTH injection (P=0.0001) and handling (P<0.0001). The time to reach peak FCM concentrations after ACTH injection tended to differ between groups (P=0.055) averaging (±SE) 11.0±1.04, 10.6±1.30 and 7.8±0.20h for vixens, juvenile females and juvenile males, respectively. After handling, peak FCM values were reached after 10.1±0.55h with no significant differences between groups. Peak concentrations averaged 2143±264ng/g after the ACTH and 1008±128ng/g after handling, compared to 475±48ng/g for baseline levels. Peak FCM values tended to vary between individuals more in females than in males. Baseline FCM concentrations prior to handling were, unexpectedly, higher in more confident foxes (P=0.004), a finding perhaps indicating a potential preparative role of cortisol in silver foxes. There was also a negative trend between foxes’ confidence and their times to reach peak FCM concentrations after handling (P=0.062), suggestive of a prolonged adrenocortical activation in more fearful individuals. Based on the rates that foxes produce faecal samples and the times to reach maximum FCM concentrations, we suggest a four hour delay to first faeces collection, before collecting samples every third hour the next 12 following hours to monitor elevations after an acute stressor. Our study confirms faecal cortisol metabolites as a valid indicator of adrenocortical activity in farmed silver foxes.

Prevalence of Pentatrichomonas hominis infections in six farmed wildlife species in Jilin, China

Pentatrichomonas hominis is an anaerobic flagellated protozoan that primarily parasitizes the gastrointestinal tract and is a conditional pathogen. It has an extensive host range and is well known as a potential causative agent of zoonotic disease. The objective of this study was to provide the first findings of the prevalence of P. hominis in six farmed wildlife species, sika deer (S.D.), Rex rabbits (R.R.), blue foxes (B.F.), silver foxes (S.F.), raccoon dogs (R.D.) and minks (M.), that are commercially important in Jilin Province, China. In this study, 450 faecal samples were tested for P. hominis infection by culturing and nested PCR assays. The average prevalence of P. hominis infections were as follows: S.D. 20% (26/130), R.R. 16.25% (13/80), B.F. 45% (27/60), S.F. 43.33% (26/60), R.D. 53.33% (32/60) and M. 48.33% (29/60). The prevalence in herbivores (18.57% for S.D. and R.R.) was significantly lower than that in non-herbivores (47.5%). PCR product sequencing indicated that infections were mainly caused by the P. hominis strain Changchun Canine 1, and we found a P. hominis strain with a mutated sequence, Changchun-RR, which had three mutations compared with the referenced homologous P. hominis sequences. Morphological observations of the Changchun-RR strain showed that it was similar to P. hominis. Our study suggests that P. hominis is widespread in six farmed wildlife species in Jilin Province and provides baseline information for the presence of this parasite in these animals.

The Potential Role of Antigen Priming In Increasing the Overall Antimicrobial Resistance in Captive Silver Foxes

Abstract: Objective: We hypothesized antigenic priming should stimulate the humoral and cell-mediated adaptive immunity, further improved by vegetal extracts, alleviating the immune suppression induced by captivity stress in silver foxes. Material and Methods: One of two groups of adult silver foxes was sc primed and boosted 7 days later with a 5% SRBC suspension. Serum antibody titers (hemagglutination test) and circulating immune complexes levels (4.2% PEG precipitation) were quantified and ln of the antibody titers were calculated seven days later. An in vitro blast transformation test was carried out on blood samples using alcoholic extracts of C. officinalis, A. montana, S. officinale, Echinaceea spp. and immune stimulating compounds and glucose consumption was evaluated. The significance of the differences was interpreted by Student’s t-test. Results: Cells grew better in primed foxes versus the unprimed individuals (68.8±9.88 and 17.49±22.9). The primed animals reacted significantly (p< 0.001-p< 0.01) better to vegetal extracts (C. officinalis, E. angustifolia) and to thymus extract, selenium salts and bovine tuberculin. Anti-SRBC antibodies were highly variable (0.69 - 5.54). Conclusion: SRBC exerted a positive effect on both humoral and cell-mediated immune responses in silver foxes, supporting the enhancement of antimicrobial defense by booster vaccination and immune stimulating therapy. Key words: Silver Foxes, Antigenic Stimulation, Adaptive Immunity, Vegetal Extracts.

Humans identify negative (but not positive) arousal in silver fox vocalizations: implications for the adaptive value of interspecific eavesdropping.

The ability to identify emotional arousal in heterospecific vocalizations may facilitate behaviors that increase survival opportunities. Crucially, this ability may orient inter-species interactions, particularly between humans and other species. Research shows that humans identify emotional arousal in vocalizations across multiple species, such as cats, dogs, and piglets. However, no previous study has addressed humans’ ability to identify emotional arousal in silver foxes. Here, we adopted low- and high-arousal calls emitted by three strains of silver fox—Tame, Aggressive, and Unselected—in response to human approach. Tame and Aggressive foxes are genetically selected for friendly and attacking behaviors toward humans, respectively. Unselected foxes show aggressive and fearful behaviors toward humans. These three strains show similar levels of emotional arousal, but different levels of emotional valence in relation to humans. This emotional information is reflected in the acoustic features of the calls. Our data suggest that humans can identify high-arousal calls of Aggressive and Unselected foxes, but not of Tame foxes. Further analyses revealed that, although within each strain different acoustic parameters affect human accuracy in identifying high-arousal calls, spectral center of gravity, harmonic-to-noise ratio, and F0 best predict humans’ ability to discriminate high-arousal calls across all strains. Furthermore, we identified in spectral center of gravity and F0 the best predictors for humans’ absolute ratings of arousal in each call. Implications for research on the adaptive value of inter-specific eavesdropping are discussed.

First description of Cryptosporidium ubiquitum XIIa subtype family in farmed fur animals

This study investigated the prevalence of Cryptosporidium in farmed fur animals in the Czech Republic and Poland. A total of 480 faecal samples were collected from fur animals, including 300 American mink (Mustela vison), 60 silver foxes (Vulpes vulpes), 50 long-tailed chinchillas (Chinchilla lanigera), and 70 nutrias (Myocastor coypus), at 14 farms. Samples were examined for the presence of Cryptosporidium using microscopy (following aniline-carbol-methyl violet staining) and sequence analysis of PCR amplified products. Three mink and two chinchillas from two different farms tested positive for Cryptosporidium ubiquitum DNA. The presence of C. ubiquitum DNA was not associated with diarrhoea. Subtyping of C. ubiquitum isolates by sequence analysis of the 60-kDa glycoprotein gene showed that isolates belonged to the XIIa subtype family, which was previously restricted to humans and ruminants. This suggests that C. ubiquitum subtype XIIa has a broader host range than previously reported.

Facial shape differences between rats selected for tame and aggressive behaviors.

Domestication has been consistently accompanied by a suite of traits called the domestication syndrome. These include increased docility, changes in coat coloration, prolonged juvenile behaviors, modified function of adrenal glands and reduced craniofacial dimensions. Wilkins et al recently proposed that the mechanistic factor underlying traits that encompass the domestication syndrome was altered neural crest cell (NCC) development. NCC form the precursors to a large number of tissue types including pigment cells, adrenal glands, teeth and the bones of the face. The hypothesis that deficits in NCC development can account for the domestication syndrome was partly based on the outcomes of Dmitri Belyaev’s domestication experiments initially conducted on silver foxes. After generations of selecting for tameness, the foxes displayed phenotypes observed in domesticated species. Belyaev also had a colony of rats selected over 64 generations for either tameness or defensive aggression towards humans. Here we focus on the facial morphology of Belyaev’s tame, ‘domesticated’ rats to test whether: 1) tameness in rats causes craniofacial changes similar to those observed in the foxes; 2) facial shape, i.e. NCC-derived region, is distinct in the tame and aggressive rats. We used computed-tomography scans of rat skulls and landmark-based geometric morphometrics to quantify and analyze the facial skeleton. We found facial shape differences between the tame and aggressive rats that were independent of size and which mirrored changes seen in domesticated animals compared to their wild counterparts. However, there was no evidence of reduced sexual dimorphism in the face of the tame rats. This indicates that not all morphological changes in NCC-derived regions in the rats follow the pattern of shape change reported in domesticated animals or the silver foxes. Thus, certain phenotypic trends that are part of the domestication syndrome might not be consistently present in all experimental animal models.

Expression of the DNA methyltransferase genes in silver foxes experimentally selected for domestication

Animal domestication is a model of a rapid evolutionary process. In experimental fox domestication, the time required for the emergence and fixation of specific evolutionary changes was reduced from thousands to tens of years, compared to historical domestication. Tame foxes were obtained by extreme selective breeding for emotionally positive response toward humans. Unselected foxes, as well as foxes bred for enhanced aggressiveness to humans were used as control. Epigenetic regulation of gene expression is considered as one of the possible mechanisms of rapid evolution. In this study, expression of DNA methyltransferase genes, DNMT1 and DNMT3A, was investigated. It was demonstrated that, in tame foxes, the level of DNMT3A gene expression in the prefrontal cortex, hippocampus, and spleen was increased by more than 2 times in comparison with aggressive and unselected foxes. At the same time, the DNMT1 expression level did not differ among the studied groups of animals. A possible reason for the differences found in the DNMT3A expression could be the changes in the level and metabolism of methionine, which serves as a donor of methyl groups during DNA methylation. However, this study showed that there were no differences in the serum methionine levels between tame, unselected, and aggressive foxes. Thus, the data support the hypothesis that selection for positive emotional response toward humans affected the DNA methylation machinery.

Behavioral and cardiopulmonary effects of dexmedetomidine–midazolam and dexmedetomidine–midazolam–butorphanol in the silver fox (Vulpes vulpes)

ObjectiveTo evaluate the behavior and some cardiopulmonary variables of dexmedetomidine–midazolam or dexmedetomidine–midazolam-butor-phanol in the silver fox (Vulpes vulpes). Study designBlinded, randomized design. AnimalsSixteen adult silver foxes, aged 7–9 months, weighting 6.0–9.2 kg. MethodsAnimals were randomly assigned to dexmedetomidine (50 μg kg−1) and midazolam (0.45 mg kg−1) (group DM) or to dexmedetomidine (30 μg kg−1), midazolam (0.45 mg kg−1) and butorphanol (0.25 mg kg−1) (group DMB), administered intramuscularly. Pulse rate (PR), respiratory rate (fR), noninvasive arterial pressures, oxygen saturation (SpO2), rectal temperature (T) and behavioral scores (posture, sedation, antinociception, jaw relaxation and auditory response) were measured at 5, 10, 20, 30, 40, 50 and 60 minutes after injection. Time from drug injection to recumbency with no response to stimuli (IT) and time from administration of atipamezole (0.2 mg kg−1) to standing with coordination (RT) were recorded. The occurrences of adverse events were recorded. Data were analyzed by two-tailed unpaired t-tests and Bonferroni post hoc tests. Significant differences were accepted at p<0.05. ResultsThere were no statistically significant differences between the groups for IT or RT. Arterial pressures were higher in DMB at each time point except at 5 minutes. PR was lower in DM at each time point except at 10 and 60 minutes. No significant difference was found between the groups for fR, SpO2 and T. The behavioral scores were significantly lower (lower quality immobilization) in DMB at 5,10 and 60 minutes. Conclusions and clinical relevanceIT and RT were not different between the groups. Both protocols provided immobilization for 30–40 minutes with excellent muscle relaxation and analgesia adequate for clinical examinations and some simple surgical procedures.

The domestication and the brain: forty years after

The domestication of animals was crucial for the civilization evolutionary experiment. The main characteristic of domesticated animal is tame behavior towards man. D.K. Belyaev suggested that the domestication was carried out by man of the Stone Age as unintended selection of nonaggressive animals. This hypothesis was confirmed at the Institute of Cytology and Genetics, Novosibirsk, by unique long-lasting selection of silver foxes, Norway rats and American minks for nonaggressive behavior towards man. The review concentrates on the role of the brain neurotransmitters in the mechanism of animal domestication. Specifically, it describes the effect of selective breeding for nonaggressive behavior on the brain neurotransmitter serotonin (5-HT) system. Our data showed that produced by domestication the conversion of wild, aggressive animal to non-aggressive towards man is associated with changes in the expression of key molecular members determining the brain 5-HT system functioning. Significant difference between aggressive and nonaggressive animals in the 5-HT metabolism, in the expression of principle metabolic enzymes and 5-HT receptors was shown in different species of mammals (silver foxes, Norway rats and American minks). Higher concentration of 5-HT and its metabolite, 5-hydroxyindoleacetic acid, increased activity of the principle enzyme in 5-HT synthesis (tryptophan hydroxylase-2) and decreased activity of the principle enzyme in 5-HT degradation (monoamine oxidase A) was shown in the midbrain of domesticated silver foxes and rats. The expression of the 5-HTA receptor gene, the density and functional activity of 5-HTA receptors in nonaggressive rats were increased. The review provides converging lines of evidence for our hypothesis that the changes in the brain 5-HT contributes to a mechanism underlying correlative patterns of domestication, i.e. changes in the pivotal for stress response and for the reproduction pituitary-adrenal and pituitary-gonadal systems.

Effects of experimental domestication of silver foxes (Vulpes vulpes) on vocal behaviour

This paper systematizes and generalizes a research cycle devoted to studying the acoustics and vocal behaviour of silver foxes that differ in their tolerance to humans. The research revealed that 50-year selection for tameness toward people resulted in selective use by Tame foxes toward humans of two call types, pant and cackle. At the same time, the selected for aggression toward people Aggressive foxes and the non-selected for behaviour Control foxes, selectively use toward humans cough and snort. Thus, call types representing vocal indicators of friendly and aggressive behaviour of foxes toward humans have been revealed by the research. Nevertheless, experimental domestication did not change vocal behaviour of foxes toward conspecifics; all three strains did not differ by their vocal behaviour toward same-strain silver foxes. Relationship has been investigated between vocal behaviour and degree of tolerance toward people for hybrids between Tame and Aggressive foxes and for backcrosses to Tame and Aggressive foxes. Effect was estimated between fox sex and the degree of human impact on focal fox for variables of fox vocal behaviour. The research revealed the universal for mammals vocal indicators of emotional arousal that are independent of the emotional valence. Characteristics of vocal behaviour that are related with positive and negative emotional valence have been revealed. A simple and effective method for estimating animal discomfort based on ”joint calls” that takes into account the characteristics of all calls irrespective of their acoustic structure has been revealed. The obtained results provide a basis for further comparative studies of the acoustic structure and vocal behaviour for other taxa of the genus Vulpes and the related canid genera (Canis, Cuon, Lycaon).