Isotope recycling in lactating dogs (Canis familiaris)

Isotope-based techniques for the measurement of water turnover, energy expenditure, and milk intake often assume that there is no recycling of isotopes once they have left the labeled animal. In experiments involving lactating females or their suckling offspring, there are several possible routes of isotope recycling. These include the consumption of labeled milk by offspring, the ingestion of labeled excreta, and the rebreathing of exhaled labeled CO(2) or water vapor by both mother and offspring. Isotope recycling might be especially important during lactation because the offspring are in close contact with each other and their mother for prolonged periods. We show here in 24- to 30-day-old domestic dog Canis familiaris puppies that there was no detectable transfer of (18)O or (2)H from labeled to unlabeled pups in two litters (16 pups, 8 labeled, 8 unlabeled) that were weaned early and independent of their mother. However, there was a significant transfer of both isotopes from labeled to unlabeled pups and from labeled pups to their mothers in nine equivalent nursing litters of the same age (27 labeled, 26 unlabeled pups). The increases in enrichment of isotopes in unlabeled offspring were greater than the increases in enrichment of the mothers. This indicates that maternal ingestion of offspring excreta and subsequent transfer of isotope in milk is not the sole pathway of recycling. Additional routes must also be important, such as exchange of isotope between pups on saliva-coated nipples and perhaps direct ingestion of excreta by unweaned young. Recycling is unlikely to be an important factor when determining maternal metabolic rate during peak lactation in domestic dogs. However, experiments that are designed to assess the energy demands of pups and isotope-based estimates of water turnover in offspring may need to take into account any effects of isotope recycling. In a theoretical example, removing the effects of recycling increased the measured energy expenditure in pups by up to 7% and increased the calculated elimination rates of both isotopes by up to 11.1% in (18)oxygen and 10.9% in (2)hydrogen.     

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.     

Forces exerted on the ground by galloping dogs (Canis familiaris)

In quadrupedal galloping, one foot of each pair (the 'trailing' foot) is set down shortly before the other ('leading') foot. Alexander, Jayes & Ker (1980) argued that the trailing and leading feet should exert different patterns of force on the ground, to make the most effective use of tendon elasticity to reduce the energy cost of locomotion. We have used two force plates mounted in tandem in a playing field to obtain records of the forces exerted by individual feet of galloping dogs. We find that the patterns of force exerted by trailing and leading feet are much more similar than had been predicted.     

On the allometry of long bones in dogs (Canis familiaris)

The allometric relations of diameter and length of humerus, ulna, femur, and tibia of 108 specimens, from 63 different breeds of dogs and 12 specimens of wolves, were calculated by means of model II of regression or major axis method. Only for the tibia were the values of wolves included in the cluster formed for dog breeds. Consequently, separate lines of regression were calculated for the other bones. Results agree in general with the exponents predicted by the theory of geometric similarity; however, the slope obtained for femur (0.865) differed significantly from this. Morphology of the long bones of the legs does not differentiate dogs and wolves; this probably reflects secondary convergence among wolves with relatively modern breeds of dogs.     

Strategy planning in dogs (Canis familiaris) in a progressive elimination task

Domestic dogs (Canis familiaris) were administered a progressive elimination task in which they had to visit and deplete three baited sites. Dogs were brought back to the starting point after each visit to any site whether they had made a correct or an incorrect choice. In Experiment 1 (n=10) the results revealed that the dogs randomly selected among the sites when they were equidistant from the starting point whereas they relied on the least distance rule when one of sites was closer to the starting point than were the other sites. In Experiment 2 (n=12), the dogs first chose the left target when angular deviation between adjacent targets varied whether the least angular deviation was on the right of the left. Results are interpreted in terms of Gibson's hypothesis about cooperative hunters. The discussion also emphasizes comparisons with cats (i.e., solitary hunters).     

Cross modal perception of body size in domestic dogs (Canis familiaris)

While the perception of size-related acoustic variation in animal vocalisations is well documented, little attention has been given to how this information might be integrated with corresponding visual information. Using a cross-modal design, we tested the ability of domestic dogs to match growls resynthesized to be typical of either a large or a small dog to size-matched models. Subjects looked at the size-matched model significantly more often and for a significantly longer duration than at the incorrect model, showing that they have the ability to relate information about body size from the acoustic domain to the appropriate visual category. Our study suggests that the perceptual and cognitive mechanisms at the basis of size assessment in mammals have a multisensory nature, and calls for further investigations of the multimodal processing of size information across animal species.     

Mechanics of locomotion of dogs (Canis familiaris) and sheep (Ovis aries)

Records have been made of the forces exerted on the ground by dogs and a sheep, in walking, trotting, cantering and slow galloping. Film has been taken simultaneously. The difference between walking and trotting was much less marked for the sheep than for the dogs.
Step length and stride length increase as speed increases. They are expressed as functions of the Froude number.
The vertical component of the force exerted by a foot on the ground shows two main maxima in walking, except in the case of the fore feet of sheep. In this case and in other gaits there is only one main maximum. The vertical movements of the fore and hind quarters which occurred in examples of each gait have been calculated from the force records.
The force exerted by a foot on the ground changes direction in the course of a step so as to remain more or less in line with a point fixed relative to the animal, but dorsal to its back.
The force records show impact disturbances in the first 003 sec of contact of each foot with the ground.
The point of application of the force on the sole of a foot tends to move posteriorly as the force increases.
The results are discussed in relation to a theoretical account of the mechanics of locomotion on legs.     

Molecular systematics of Mesocestoides sPP (cestoda: mesocestoididae) from domestic dogs (Canis familiaris) and coyotes (Canis latrans)

The genus Mesocestoides Vaillant, 1863 includes tapeworms of uncertain phylogenetic affinities and with poorly defined life histories. We previously documented 11 cases of peritoneal cestodiasis in dogs (Canis familiaris L.) in western North America caused by metacestodes of Mesocestoides spp. In the current study, DNA sequences were obtained from metacestodes collected from these dogs (n = 10), as well as proglottids from dogs (n = 3) and coyotes (Canis latrans Say, 1823 [n = 2]), and tetrathyridia representing laboratory isolates of M. corti (n = 3), and these data were analyzed phylogenetically. Two nuclear genetic markers, 18S ribosomal DNA and the second internal-transcribed spacer (ITS 2), were sequenced. Phylogenetic analysis of the 18S rDNA data recovered a monophyletic group composed of all samples of Mesocestoides spp., distinct from closely related outgroup taxa (Amurotaenia Akhmerov, 1941 and Tetrabothrius Rudolphi, 1819). Initial analysis of the ITS 2 data resolved 3 clades within Mesocestoides. Two proglottids from dogs formed a basal clade, a second clade was represented by tetrathyridial isolates, and a third clade included all other samples. Interpretation of these data from an apomorphy-based perspective identified 6 evolutionary lineages. We also assessed whether metacestodes from dogs (n = 4) are capable of asexual proliferation in laboratory mice. One tetrathyridial and 2 acephalic isolates from dogs proliferated asexually. Further investigation is warranted to determine which of the lineages represent distinct species and to determine the life history strategies of Mesocestoides spp.     

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.     

Intranasal oxytocin and a polymorphism in the oxytocin receptor gene are associated with human-directed social behavior in golden retriever dogs

The oxytocin system may play an important role in dog domestication from the wolf. Dogs have evolved unique human analogue social skills enabling them to communicate and cooperate efficiently with people. Genomic differences in the region surrounding the oxytocin receptor (OXTR) gene have previously been associated with variation in dogs' communicative skills. Here we have utilized the unsolvable problem paradigm to investigate the effects of oxytocin and OXTR polymorphisms on human-directed contact seeking behavior in 60 golden retriever dogs. Human-oriented behavior was quantified employing a previously defined unsolvable problem paradigm. Behaviors were tested twice in a repeated, counterbalanced design, where dogs received a nasal dose of either oxytocin or saline 45 min before each test occasion. Buccal DNA was analysed for genotype on three previously identified SNP-markers associated with OXTR. The same polymorphisms were also genotyped in 21 wolf blood samples to explore potential genomic differences between the species. Results showed that oxytocin treatment decreased physical contact seeking with the experimenter and one of the three polymorphisms was associated with degree of physical contact seeking with the owner. Dogs with the AA-genotype at this locus increased owner physical contact seeking in response to oxytocin while the opposite effect was found in GG-genotype individuals. Hence, intranasal oxytocin treatment, an OXTR polymorphism and their interaction are associated with dogs' human-directed social skills, which can explain previously described breed differences in oxytocin response. Genotypic variation at the studied locus was also found in wolves indicating that it was present even at the start of dog domestication.     

甘肃白水江国家级自然保护区林缘社区饲养犬只对大熊猫时空节律的影响

人类对于野生动物的影响复杂多样, 其中家养动物所产生的干扰往往被忽视, 例如保护区林缘社区饲养的家犬。半散放的家犬(Canis familiaris)进入野生动物栖息地, 对保护区内以大熊猫(Ailuropoda melanoleuca)为代表的野生动物可能产生重要影响。为明确家犬进入林区活动范围对大熊猫的影响, 本研究采用红外相机技术和GPS项圈无线追踪技术对甘肃白水江国家级自然保护区内家犬对大熊猫潜在栖息地范围和时间节律的影响进行研究, 利用MaxEnt模型对家犬活动范围及大熊猫潜在栖息地进行预测。结果表明: 甘肃白水江国家级自然保护区内大熊猫潜在栖息地面积为885.8 km², 约占保护区总面积的48.2%; 家犬活动面积为861.2 km², 约占保护区总面积的47.6%。家犬活动范围与大熊猫潜在栖息地重叠的面积约占保护区面积的28.2%, 且多集中在低海拔的常绿阔叶林。大熊猫在有家犬出现的位点和没有家犬出现的位点日活动节律具有显著差异。本研究揭示了家犬进入林区对大熊猫栖息地潜在影响的空间范围, 为保护区开展生物多样性管理提供了关键信息, 对于其他保护区具有借鉴意义。     

Hemispheric specialization in domestic dogs (Canis familiaris) for processing different types of acoustic stimuli

Lateralization is considered to be a fundamental feature of vertebrate brains. The aim of the present study was to examine the impact of functional cerebral asymmetry on processing of auditory stimuli in the domestic dog (Canis familiaris) during the orientation reaction. The experiment was conducted on 46 dogs (25 females and 21 males). Four types of auditory stimuli were used in the experiment (three meaningful stimuli: cat meowing, dog barking, the "sit" command ("siad" in Polish), and a neutral word ("wir", meaning "whirl" in Polish). It was predicted that the orientation reaction (turning the head towards the stimuli) would take place only in the case of meaningful sounds. It was also expected that dogs would show consistent lateralization. As predicted, all three meaningful stimuli elicited the orientation reaction. The response of the examined dogs to cat meowing showed significant lateralization with dominant leftwards movement, which hints towards activation of the right cerebral hemisphere and may be related to strong emotions evoked by this stimulus. Contrary to results of previous studies, dogs reacting to dog barking turned their heads leftwards more often, which suggests activation of the right cerebral hemisphere, probably related to the emotional meaning of the stimulus. The "sit" command consistently evoked the orientation reaction but there was no significant lateralization of this movement.     

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.     

How dogs lap: ingestion and intraoral transport in Canis familiaris

It has recently been suggested that the mechanism for lifting liquid from a bowl into the oral cavity during lapping is fundamentally different in cats and dogs: cats use adhesion of liquid to the tongue tip while dogs 'scoop' with their backwardly curled tongue. High-speed light videos and X-ray videos show that on the contrary, both cats and dogs use the mechanism of adhesion. Liquid is transported through the oral cavity to the oesophagus, against gravity, on the surface of the tongue as it is drawn upwards, then a tight contact between the tongue surface and palatal rugae traps liquid and prevents its falling out as the tongue is protruded. At least three cycles are needed for intraoral transport of liquid in the dog.     

Comparison of rectal and vaginal temperature daily rhythm in dogs (Canis familiaris) under different photoperiod

To investigate the daily rhythm of rectal and vaginal temperature, we used six mongrel dogs with a mean body weight of 15±3 kg, aged between 2 and 3 years old. Rectal and vaginal temperatures were recorded every 3 h over 48-h period during three different lighting regimes: natural light/dark (L/D) cycle (sunrise 06:25, sunset 17:05), constant light (L/L) and constant darkness (D/D). A daily rhythm of rectal temperature was observed in both days of monitoring in all experimental conditions. Vaginal temperature showed a daily rhythmicity in L/D and D/D cycle. During the L/L cycle, daily rhythm was disrupted. Rhythmic parameters (MESOR, amplitude, acrophase and robustness) did not change between the different photoperiod and the site of temperature collection. In conclusion, the monitoring of vaginal temperature can be considered a valid alternative to the monitoring of body temperature as well as rectal temperature under natural lighting conditions in canine medicine.     

Effect of reinforcement, reinforcer omission and extinction on a communicative response in domestic dogs (Canis familiaris)

There is a controversy about the mechanisms involved in the interspecific communicative behaviour in domestic dogs. The main question is whether this behaviour is a result of instrumental learning or higher cognitive skills are required. The present investigations were undertaken to study the effect of learning processes upon the gaze towards the human's face as a communicative response. To such purpose, in Study 1, gaze response was subjected to three types of reinforcement schedules: differential reinforcement, reinforcer omission, and extinction in a situation of “asking for food”. Results showed a significant increase in gaze duration in the differential reinforcement phase and a significant decrease in both the omission and extinction phases. These changes were quite rapid, since they occurred only after three training trials in each phase. Furthermore, extinction resulted in animal behaviour changes, such as an increase in the distance from the experimenter, the back position and lying behaviour. This is the first systematic evaluation of the behavioural changes caused by reward withdrawal (frustration) in dogs. In Study 2, the gaze response was studied in a situation where dogs walked along with their owners/trainers. These results show that learning plays an important role in this communicative response. The possible implications of these results for service dogs are discussed.