A Comparison of the Sensory Development of Wolves (Canis lupus lupus) and Dogs (Canis lupus familiaris)

Little is known about the development of the sensory systems of wolves. The timing of sensory development in wolves is usually extrapolated from studies on dogs, since they are members of the same species. However, early developmental differences between these two subspecies have already been identified. For example, wolves tend to approach and investigate objects in their environment 2 wk before dogs. These changes in developmental timing may play an important role in the behavioral differences between adult wolves and dogs. The purpose of this study is to compare the development of the sensory systems in wolves and dogs. Responses of seven wolf pups and 43 dog pups to familiar and novel olfactory, auditory, and visual stimuli were tested weekly from 2–7 wk of age. Eleven wolf pups were also observed for orientation towards auditory and visual stimuli during 2‐h sessions, 5 d a week, from 2–8 wk of age. These observations were supplemented by the daily records of caretakers. The results suggest that wolves and dogs both develop olfaction by 2 wk, audition by 4 wk, and vision by 6 wk on average, despite the 2‐wk shift in their ability to explore. This means that when wolves begin to explore at 2 wk, they are blind and deaf, and must rely primarily on their sense of smell. Thus, there is a significant alteration of how these subspecies experience their environment during the critical period of socialization. These findings lead to an alternative explanation for the difference in dogs' and wolves' abilities to form interspecies social attachments, such as those with humans.     

Peptidergic regulation of feeding in the dog (Canis familiaris)

Although the incidence of obesity in the domesticated dog is high, few studies have investigated the regulation of food intake in this species. In the present study we investigated the response of the dog to a number of putative satiety agents including cholecystokinin (CCK), bombesin, calcitonin and naloxone. CCK significantly suppressed food intake during a scheduled fifteen minute meal in intact dogs and in dogs receiving total subdiaphragmatic vagotomies. Emesis occurred following injection of higher doses of CCK in most dogs. Bombesin and calcitonin reduced intake in both normal and vagotomized dogs, although higher doses of calcitonin were needed to significantly suppress feeding in vagotomized dogs compared with intact animals. Naloxone reduced feeding by as much as 60% in intact and vagotomized animals. Glucagon suppressed feeding in intact dogs, but not in vagotomized animals. Somatostatin and pancreatic polypeptide did not alter food intake. Thus the domesticated dog responds somewhat differently to some neuropeptides compared with the laboratory rat stressing the importance of examining the regulation of food intake across species.     

Lateralised behaviour in the domestic dog,Canis familiaris

Paw use on three tasks in 53 domestic dogs (Canis familiaris) was studied to determine whether the animals exhibited a significant paw preference, and, if so, to explore the direction and strength of the dogs' preferred paw use, both within, and between, tasks. The influence of the dogs' sex on their paw preferences was also explored. The findings revealed that lateralised behaviour was strongly sex related. Male and female showed paw preferences at the level of the population but in opposite directions. Female dogs had a greater preference for using their right paw on all tasks, whilst males were more inclined to adopt their left paw. Analysis revealed significant positive relationships for two of a possible three intertask correlations. Overall, the findings suggest that there are two distinct populations of paw preference in the domestic dog that cluster around the animals' sex. It is recommended that further work be conducted to explore the influence of pre-training on dogs' paw preferences before generalisations regarding laterality in this species are drawn.     

General assessment of copy number variation in normal and tumor tissues of the domestic dog (Canis lupus familiaris)

In recent years, characterization of a copy number variation (CNV) of the genomic DNA has provided evidence for the relationship of this type of genetic variation with the occurrence of a broad spectrum of diseases, including cancer lesions. Copy number variants (CNVs) also occur in the genomes of healthy individuals as a result of abnormal recombination processes in germ cells and have a hereditary character contributing to the natural genetic diversity. Recent image analysis methods and advanced computational techniques allow for identification of CNVs using SNPs genotyping microarrays based on the analysis of signal intensity observed for markers located in the specific genomic regions. In this study we used CanineHD BeadChip assay (Illumina) to identify both natural and cancer-induced CNVs in the genomes of different dog breeds and in different cancer types occurring in this species. The obtained results showed that structural aberrations are a common phenomenon arising during a tumor progression and are more complex and widespread in tumors of mesenchymal tissue origin than in epithelial tissue originating tumors. The tumor derived CNVs, in comparison to healthy samples, were characterized by larger sizes of regions, higher number of amplifications, and in some cases encompassed genes with potential effect on tumor progression.     

The mechanics of jumping by a dog (Canis familiaris)

A force platform has been used to obtain records of the forces exerted on the ground by an Alsatian dog, during take-off for running long jumps and standing scale jumps. The records have been analysed in conjunction with cinematograph film, taken simultaneously, and anatomical data. Stresses in the principal muscles of the hind limb, and in the triceps, have been calculated and the values obtained are compared with the stresses found by other investigators in isometric experiments with excised mammal muscles. Stresses in certain tendons and bones have been calculated, and the values obtained are compared with published values for the strength of tendon and bone. Evidence is presented that the gastrocnemius and plantaris muscles behave, in take-off for a jump, essentially as passive elastic bodies. Most of the elastic energy is probably stored in their tendons. A tendency for distal limb muscles to be pinnate, with much shorter fibres than proximal limb muscles, is noted and discussed.     

Interspecies hormonal interactions between man and the domestic dog (Canis familiaris)

To date, hormonal influence in interspecies interaction has not been examined. In a study of a dog agility competition among human/dog teams, men's pre-competition basal testosterone (T) levels were positively related to changes in dogs' cortisol levels from pre- to post-competition, but only among losing teams. Furthermore, pre-competition basal T in men on losing teams predicted more than half of the variance in dogs' cortisol change. This relationship was mediated through men's punitive and affiliative behaviors towards their dogs immediately after competition. Men's T change was also a significant predictor of dogs' change in cortisol such that men who experienced greater decreases in T after a loss were associated with dogs that experienced greater increases in cortisol. In winning teams, men's pre-competition T and T changes were unrelated to dogs' cortisol changes. These results are discussed in light of T as a proxy for dominance motivation as well as T's relation to stress across the species boundary.     

Analysis of major repetitive DNA sequences in the dog (Canis familiaris) genome

A systematic screening and analysis of repeated DNA sequences from a dog genomic library composed of small DNA inserts enabled us to characterize abundant canine repetitive DNA families. Four main families were identified: i) a group of highly repeated tRNA-derived short interspersed repetitive DNA elements (tRNA-SINEs); ii) another type of SINE-like element that was mainly found inserted into long interspersed repetitive elements (LINEs); iii) LINEs of the L1 type; and iv) satellite or satellite-like DNA. Surprisingly, no SINEs derived from 7SL RNA were found in the dog genome. These data should help in the analysis of canine DNA sequences and in the design of canine genome mapping reagents. Received: 4 November 1998 / Accepted: 2 February 1999     

The ligaments and menisci of the femorotibial joint of the wolf (Canis lupus L., 1758)--anatomic and functional analysis in comparison with the domestic dog (Canis lupus f. familiaris)

Based on dissection of 11 (4 m and 7f) adult wolves (Canis lupus L., 1758) kept in captivity, the morphology and mechanics of the ligaments and menisci of the femorotibial joint are described. Compared with the anatomical data of the dog (Canis lupus f. familiaris), the differences are discussed with respect to their importance for functional considerations.     

A radiation hybrid map of the X-chromosome of the dog (Canis familiaris)

The dog serves as an animal model for several human diseases including X-chromosome diseases. Although the canine X-chromosome is one of the largest chromosomes in the dog, only a few markers have been mapped to it to date. Using a commercially available canine whole genome radiation hybrid (RH) panel we have localized 14 microsatellite markers, 18 genes and 13 STSs on the canine X-chromosome, extending the total number of mapped markers to 45 covering an estimated 830 cR. Out of these 45 markers, seven distinct groups of markers could be established with an average spacing of 18.8 cR(3000) and ten markers remained unlinked. Using FISH analysis, six markers could be mapped physically to the p- or q-arm of the X-chromosome. Combined with the FISH mapping, three RH groups could be assigned to the p-arm and two RH groups to the q-arm. Comparison with the human X-chromosome map revealed conserved synteny up to 234 cR (TIMP1-ALAS2-AR-IL2RG-XIST). We show here that the similarity of the canine and human X-chromosomes is the largest for any mammalian species beyond the primates.     

The application of FISH techniques for physical mapping in the dog (Canis familiaris)

The abundance of CA/GT repeats in the DNA of the dog (Canis familiaris) has established the importance of polymorphic microsatellites in the development of a low density map of the canine genome. The assignment of linkage groups of markers to chromosomes by physical mapping requires reliable cytogenetic techniques for routine production of metaphase cells. The dog has 78 chromosomes, many of which are smaller and more contracted than those of other mammals. Although the molecular study of inherited disease in dogs has important implications for both improved welfare in dogs and the provision of animal models for human diseases, the small size and large number of chromosomes in the canine genome has discouraged the inclusion of cytogenetic analysis in the planning of relevant research protocols. In this report, Fluorescence In Situ Hybridization (FISH) techniques have been optimized for the physical mapping of probes in C. familiaris. A method to obtain a good yield of early and midmetaphases from short-term peripheral blood cultures and the optimal conditions for hybridization and detection of probes is described. Thirteen microsatellite-containing cosmid probes from a canine genomic library in pWE15, a highly repetitive probe (human ribosomal DNA pHr14E3), and a human X Chromosome (Chr) paint have been mapped. Six microsatellites, two ribosomal sites, and the human paint have been assigned to specific chromosomes. Received: 5 June 1995 / Accepted: 1 September 1995     

Energetics of lactation in domestic dog (Canis familiaris) breeds of two sizes

The energetics of lactation was measured in two breeds of domestic dog during peak lactation. Labrador Retrievers (30 kg) had larger litter sizes than Miniature Schnauzers (6 kg). During the 7-day experimental period, Labrador pups increased more in mass than Schnauzer pups, both absolutely and relatively. Consequently, the energy demands of the litter, relative to maternal metabolism, were higher in Labradors than Schnauzers. Milk composition and gross efficiency of milk production were not significantly different between breeds and the costs of lactation were fuelled by increases in food intake. Metabolisable energy intake was higher than predicted in Labradors, but lower than predicted in Schnauzers. These patterns differ from interspecific expectations, which would predict larger animals to reproduce more slowly, have smaller litter sizes, and invest less energy in reproduction.     

Arterial supply to the stomach of indigenous dog (Canis familiaris) in Bangladesh.

Arterial supply to the stomach of dogs indigenous to Bangladesh was investigated by using latex. The hepatic, left gastric and splenic arteries sent their major branches to the stomach. The cranial and caudal branches of the left gastric artery supplied the lesser curvature of the stomach. The right gastric, and right and left gastroepiploic arteries also sent their branches to both the lesser and greater curvatures. Six or seven short gastric arteries from the splenic artery supplied the greater curvature. Anastomoses between the left and right gastric, between the left and right gastroepiploic, and between short gastric arteries and left gastric arteries were observed.     

When dogs look back: inhibition of independent problem-solving behaviour in domestic dogs (Canis lupus familiaris) compared with wolves (Canis lupus)

Domestic dogs have been recognized for their social sensitivity and aptitude in human-guided tasks. For example, prior studies have demonstrated that dogs look to humans when confronted with an unsolvable task; an action often interpreted as soliciting necessary help. Conversely, wolves persist on such tasks. While dogs'' ‘looking back’ behaviour has been used as an example of socio-cognitive advancement, an alternative explanation is that pet dogs show less persistence on independent tasks more generally. In this study, pet dogs, shelter dogs and wolves were given up to three opportunities to open a solvable puzzle box: when subjects were with a neutral human caretaker, alone and when encouraged by the human. Wolves were more persistent and more successful on this task than dogs, with 80% average success rate for wolves versus a 5% average success rate for dogs in both the human-in and alone conditions. Dogs showed increased contact with the puzzle box during the encouragement condition, but only a moderate increase in problem-solving success. Social sensitivity appears to play an important role in pet and shelter dogs'' willingness to engage in problem-solving behaviour, which could suggest generalized dependence on, or deference to, human action.     

Anatomical closure of the ductus arteriosus in the dog (Canis familiaris).

The ductus arteriosus was studied in 138 dogs (80 female and 58 male) aged from 6 h to 21 days. This experiment led us to conclude that the anatomical closure of the d. arteriosus starts within 96 h and is obliterated after 6 days in 100% of the animals studied. We have also evidenced that the closure starts in the medial part of the d. arteriosus and progresses to the pulmonary artery and aorta.     

Pregnancy-specific elevations in fecal concentrations of estradiol, testosterone and progesterone in the domestic dog (Canis familiaris)

Estradiol (E2), testosterone (T) and progesterone (P4) concentrations were determined by enzyme-immunoassay in aqueous extracts of fecal samples obtained during anestrus, proestrus, estrus and metestrus of 11 nonpregnant and 11 pregnant bitches. Fecal hormone concentrations (ng/g) changed in relation to stage of cycle. Mean fecal steroid concentrations in 22 anestrous bitches and 3 ovariectomized bitches were low and similar for E2 (53 +/- 5 and 27 +/- 2), T (60 +/- 7 and 36 +/- 6), and P4 (62 +/- 6 and 86 +/- 15). Within 0 to 3 d of the ovulatory LH surge fecal E2 reached peak concentrations (301 +/- 38). The T peaks (281 +/- 41) were coincident or 1 to 3 d later. Fecal P4 was then elevated for approximately 2 m.o. Between Days 26 and 45 after ovulation, mean fecal P4 concentrations were higher (P < 0.05) in pregnant (401 +/- 60) than in nonpregnant bitches (164 +/- 23) and peak fecal P4 concentrations in individual animals were higher (P < 0.01) in pregnant (812 +/- 121) than in nonpregnant bitches (425 +/- 97). In the same period mean concentrations of E2 (117 +/- 13 vs 61 +/- 5) and T (102 +/- 10 vs 70 +/- 6) were also higher (P < or = 0.05) in pregnant than in nonpregnant bitches. Serum E2, T and P4 concentration were positively correlated (P = 0.1) with concentration in fecal samples obtained one day after serum collection. Although serial fecal ovarian steroid concentrations demonstrate the time course of ovulatory cycles, the diagnostic value of individual fecal samples appears limited. The ratios of peak to basal values were approximately 6, 5 and 7 for E2, T and P4, respectively, and were considerably lower than ratios of 12 to 50 previously reported for serum or plasma concentrations. The results demonstrate that there are pregnancy-specific increases in P4, E2 and T production reflected in fecal concentrations. While such increases are reflected in fecal samples, they are generally not evident in serum or plasma concentrations because of increased hemodilution, metabolism and clearance in pregnant bitches. The physiological stimulus for these increases, presumably ovarian in origin, or the potential role of prolactin is not known.     

Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVI Dingo (Canis familiaris dingo) and dog (Canis familiaris)

As part of a programme of comparative measurements of P _d (diffusional water permeability) the RBCs (red blood cells) from dingo (Canis familiaris dingo) and greyhound dog (Canis familiaris) were studied. The morphologies of the dingo and greyhound RBCs [examined by light and SEM (scanning electron microscopy)] were found to be very similar, with regard to aspect ratio and size; the mean diameters were estimated to be the same (～7.2 μm) for both dingo and greyhound RBCs. The water diffusional permeability was monitored by using an Mn²⁺‐doping ¹H NMR technique at 400 MHz. The P _d (cm/s) values of dingo and greyhound RBCs were similar: 6.5×10^?3 at 25°C, 7.5×10^?3 at 30°C, 10×10^?3 at 37°C and 11.5×10^?3 at 42°C. The inhibitory effect of a mercury‐containing SH (sulfhydryl)‐modifying reagent PCMBS (p‐chloromercuribenzene sulfonate) was investigated. The maximal inhibition of dingo and greyhound RBCs was reached in 15–30 min at 37°C with 2 mmol/l PCMBS. The values of maximal inhibition were in the range 72–74% when measured at 25°C and 30°C, and ～66% at 37°C. The lowest value of P _d (corresponding to the basal permeability to water) was ～2–3×10^?3 cm/s in the temperature range 25–37°C. The E _a,d (activation energy of water diffusion) was 25 kJ/mol for dingo RBC and 23 kJ/mol for greyhound RBCs. After incubation with PCMBS, the values of E _a,d increased, reaching 46–48 kJ/mol in the condition of maximal inhibition of water exchange. The electrophoretograms of membrane polypeptides of the dingo and greyhound RBCs were compared and seen to be very similar. We postulate that the RBC parameters reported in the present study are characteristic of all canine species and, in particular in the two cases presented here, these parameters have not been changed by the peculiar Australian habitat over the millennia (as in the case of the dingo) or over shorter time periods, decades or centuries (as in the case of the domestic greyhound).