| 1. |
- Hansen Wheat, Christina, et al.
(författare)
-
Morphology does not covary with predicted behavioral correlations of the domestication syndrome in dogs
- 2020
-
Ingår i: Evolution Letters. - : Oxford University Press (OUP). - 2056-3744. ; 4:3, s. 189-199
-
Tidskriftsartikel (refereegranskat)abstract
- Domesticated animals display suites of altered morphological, behavioral, and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS). Because these alterations are observed to co-occur across a wide range of present day domesticates, the traits within the DS are assumed to covary within species and a single developmental mechanism has been hypothesized to cause the observed co-occurrence. However, due to the lack of formal testing it is currently not well-resolved if the traits within DS actually covary. Here, we test the hypothesis that the presence of the classic morphological domestication traits white pigmentation, floppy ears, and curly tails predict the strength of behavioral correlations in support of the DS in 78 dog breeds. Contrary to the expectations of covariation among DS traits, we found that morphological traits did not covary among themselves, nor did they predict the strength of behavioral correlations among dog breeds. Further, the number of morphological traits in a breed did not predict the strength of behavioral correlations. Our results thus contrast with the hypothesis that the DS arises due to a shared underlying mechanism, but more importantly, questions if the morphological traits embedded in the DS are actual domestication traits or postdomestication improvement traits. For dogs, it seems highly likely that strong selection for breed specific morphological traits only happened recently and in relation to breed formation. Present day dogs therefore have limited bearing of the initial selection pressures applied during domestication and we should reevaluate our expectations of the DS accordingly.
|
|
| 2. |
- Laikre, Linda, 1960-, et al.
(författare)
-
Planned cull endangers Swedish wolf population
- 2022
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 377:6602
-
Tidskriftsartikel (refereegranskat)abstract
- In May, the Swedish Parliament announced a goal to reduce the Swedish wolf population from about 400 to about 200 individuals (1). This action further threatens this highly endangered population, which is genetically isolated and inbred. Scientific advice for improvements has not been implemented (2, 3).The Swedish Parliament proposed this drastic cull at a time when biodiversity is a global focus. The 50-year anniversary of the first UN conference on the environment was celebrated in June, and the UN Convention on Biological Diversity (CBD) will soon finalize its global biodiversity framework for 2020 to 2050. Sweden’s actions are inconsistent with the country’s obligations under the CBD and European Union law.Few wild populations are as well studied as the Scandinavian wolf. Genetic monitoring has provided a full pedigree since the population was reestablished in the 1980s after extinction, and the data confirm persisting genetic isolation (4–6). Hunting, conducted both legally and illegally, has prevented population expansion and the influx of genetic variation.Three founders comprised the population’s genetic origin until 2007, and only three more wolves have subsequently contributed genetically to the present population (6). The genetic base is thus extremely narrow, and genomic erosion has been confirmed (7, 8). The average level of inbreeding is similar to the level found in the offspring of two full siblings (6). Inbreeding in this population has been shown to reduce litter size (4). Also, high frequencies of anatomical defects (9) and male reproductive disorders (10) have been observed.To make this population viable, population size and immigration must increase. So far, the population has been too small, and limited immigration followed by inbreeding could lead to extinction, similar to the Isle Royale wolf population (11). The goal should be to recreate a well-connected metapopulation spanning Scandinavia and Finland with a genetically effective population size of over 500, in line with the proposed CBD indicator (12). Considerably more genetic exchange than the current one-migrant-per-generation aim is needed (3).
|
|
| 3. |
- Hansen Wheat, Christina, et al.
(författare)
-
Behavioural correlations of the domestication syndrome are decoupled in modern dog breeds
- 2019
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Domestication is hypothesized to drive correlated responses in animal morphology, physiology and behaviour, a phenomenon known as the domestication syndrome. However, we currently lack quantitative confirmation that suites of behaviours are correlated during domestication. Here we evaluate the strength and direction of behavioural correlations among key prosocial (sociability, playfulness) and reactive (fearfulness, aggression) behaviours implicated in the domestication syndrome in 76,158 dogs representing 78 registered breeds. Consistent with the domestication syndrome hypothesis, behavioural correlations within prosocial and reactive categories demonstrated the expected direction-specificity across dogs. However, correlational strength varied between dog breeds representing early (ancient) and late (modern) stages of domestication, with ancient breeds exhibiting exaggerated correlations compared to modern breeds across prosocial and reactive behaviours. Our results suggest that suites of correlated behaviours have been temporally decoupled during dog domestication and that recent shifts in selection pressures in modern dog breeds affect the expression of domestication-related behaviours independently.
|
|
| 4. |
|
|
| 5. |
- Hansen Wheat, Christina, 1978-
(författare)
-
From wolf to dog: Behavioural evolution during domestication
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biologists since Darwin have recognized that domestication, where species are selected to live in human-controlled environments, exerts strong selection on organisms and dramatically impacts their evolutionary trajectories. Across domesticated mammal species, characteristic morphological, physiological and behavioural changes occur simultaneously, as correlated traits, a phenomenon known as the domestication syndrome. Key behavioural alterations are connected with the domestication syndrome, in which domesticated animals express decreased aggression and fearfulness alongside increased sociability and playfulness compared to their wild counterparts. To investigate various aspects of the behavioural implications of domestication, we used the dog (Canis familiaris) and its extant ancestor, the grey wolf (Canis lupus), as our study species. Since we currently lack quantitative confirmation that correlated changes in behaviours follow domestication, we evaluated correlations among sociability, aggression, fearfulness and playfulness in more than 90,000 dogs in Paper I. Contrary to expectations, we found weak support for behavioural correlations in modern dog breeds, but observed exaggerated effect sizes of correlations in ancient breeds. We suggest that while selection on suites of behaviour have been relevant during early dog domestication, a recent shift in selection pressures in modern dog breeds affects the expression of domestication-related behaviours independently. In Paper II we therefore contrasted the expression of sociability, aggression, fearfulness and playfulness during domestication in wolf hybrids and dogs, and found that while wolf hybrids were less playful and overall more fearful than dogs, they were not less social or more aggressive than dogs. Our results suggest that behavioral alterations during domestication do not necessarily occur in concert as predicted by the domestication syndrome and point to an important, but previously overlooked, role of selection on playfulness during the domestication of dogs. Finally, while it has been established that behavioural responses in adult domesticated animals are altered compared to ancestral species, we know little about when such species differences occur. We therefore conducted two studies addressing the effects of domestication on behavioural ontogeny. First, we examined the ontogeny of sociability, playfulness, aggression and fearfulness in wolves and dogs in Paper III and found that while wolves became less social and less playful than dogs at 12 and 16 weeks of age, we found no species differences in the development of fear. Our results suggest that the alteration of behaviours in the domestication syndrome do not develop simultaneously, and that species differences in fear might not occur until later in ontogeny. Then, in Paper IV we present the first extended examination of the development of fear behaviour in wolves and dogs throughout their first 26 weeks of life. We found that while dogs, but not wolves, expressed decreased fear towards novelty with age, this did not result in a species difference in fear response until 26 weeks of age. Our results suggest that differences in fear expression between wolves and dogs occur late during juvenile development and are caused by a loss of sensitivity towards novelty with age in dogs. Together, the four papers in this thesis highlight the need for a re-evaluation of the behaviours hypothesized to be shaped by domestication.
|
|
| 6. |
- Hansen Wheat, Christina, 1978-, et al.
(författare)
-
Human-directed attachment behavior in wolves suggests standing ancestral variation for human-dog attachment bonds
- 2022
-
Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 12:9
-
Tidskriftsartikel (refereegranskat)abstract
- Domesticated animals are generally assumed to display increased sociability toward humans compared to their wild ancestors. Dogs (Canis familiaris) have a remarkable ability to form social relationships with humans, including lasting attachment, a bond based on emotional dependency. Since it has been specifically suggested that the ability to form attachment with humans evolved post-domestication in dogs, attempts to quantify attachment behavior in wolves (Canis lupus) have subsequently been performed. However, while these rare wolf studies do highlight the potential for wolves to express human-directed attachment, the varied methods used and the contrasting results emphasize the need for further, standardized testing of wolves. Here, we used the standardized Strange Situation Test to investigate attachment behavior expressed in wolves and dogs hand-raised and socialized under standardized and identical conditions up until the age of testing. We found that 23-week-old wolves and dogs equally discriminated between a stranger and a familiar person, and expressed similar attachment behaviors toward a familiar person. Additionally, wolves, but not dogs, expressed significantly elevated stress-related behavior during the test, but this stress response was buffered by the presence of a familiar person. Together, our results suggest that wolves can show attachment behaviors toward humans comparable to those of dogs. Importantly, our findings demonstrate that the ability to form attachment with humans exists in relatives of the wild ancestor of dogs, thereby refuting claims that this phenotype evolved after dog domestication was initiated.
|
|
| 7. |
- Hansen Wheat, Christina, et al.
(författare)
-
Rearing condition and willingness to approach a stranger explain differences in point following performance in wolves and dogs
- 2023
-
Ingår i: Learning and Behavior. - : Springer Science and Business Media LLC. - 1543-4494 .- 1543-4508. ; 51:2, s. 127-130
-
Tidskriftsartikel (refereegranskat)abstract
- The relative importance of adaptation and individual ontogenetic experience in dogs’ high levels of behavioral compatibility with humans has been a topic of intense scientific attention over the past two decades. Salomons et al. Current Biology, 31, 3137–3144, (2021) recently presented a particularly rich data set of observations on both wolf and dog puppies that has the potential to contribute substantially to this debate. In their study subjecting wolf and dog puppies to batteries of tests, including the ability to follow human pointing gestures, Salomons et al. (2021) reported that dogs, but not wolves, have a specialized innate capacity for cooperation with humans. However, upon reanalyzing this data set, we reach a different conclusion—namely, that when controlling adequately for various environmental factors, wolves and dogs perform similarly in their cooperation with humans.
|
|
| 8. |
- Wheat, Christina Hansen, et al.
(författare)
-
Dogs, but Not Wolves, Lose Their Sensitivity Toward Novelty With Age
- 2019
-
Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Selection of behavioral traits holds a prominent role in the domestication of animals, and domesticated species are generally assumed to express reduced fear and reactivity toward novel stimuli compared to their ancestral species. However, very few studies have explicitly tested this proposed link between domestication and reduced fear responses. Of the limited number of studies experimentally addressing the alterations of fear during domestication, the majority has been done on canids. These studies on foxes, wolves, and dogs suggest that decreased expression of fear in domesticated animals is linked to a domestication-driven delay in the first onset of fearful behavior during early ontogeny. Thus, wolves are expected to express exaggerated fearfulness earlier during ontogeny compared to dogs. However, while adult dogs are less fearful toward novelty than adult wolves and wolf-dog hybrids, consensus is lacking on when differences in fear expression arise in wolves and dogs. Here we present the first extended examination of fear development in hand-raised dogs and European gray wolves, using repeated novel object tests from 6 to 26 weeks of age. Contrary to expectations, we found no evidence in support of an increase in fearfulness in wolves with age or a delayed onset of fear response in dogs compared to wolves. Instead, we found that dogs strongly reduced their fear response in the period between 6 and 26 weeks of age, resulting in a significant species difference in fear expression toward novelty from the age of 18 weeks. Critically, as wolves did not differ in their fear response toward novelty over time, the detected species difference was caused solely by a progressive reduced fear response in dogs. Our results thereby suggest that species differences in fear of novelty between wolves and dogs are not caused by a domestication-driven shift in the first onset of fear response. Instead, we suggest that a loss of sensitivity toward novelty with age in dogs causes the difference in fear expression toward novelty in wolves and dogs.
|
|
| 9. |
- Wheat, Christina Hansen, et al.
(författare)
-
Intrinsic Ball Retrieving in Wolf Puppies Suggests Standing Ancestral Variation for Human-Directed Play Behavior
- 2020
-
Ingår i: iScience. - : Elsevier BV. - 2589-0042.
-
Tidskriftsartikel (refereegranskat)abstract
- Domestication dramatically alters phenotypes across animal species. Standing variation among ancestral populations often drives phenotypic change during domestication, but some changes are caused by novel mutations. In dogs (Canis familiaris) specifically, it has been suggested that the ability to interpret social-communicative behavior expressed by humans originated post-domestication and this behavior is thus not expected to occur in wolves (Canis lupus). Here we report the observation of three 8-week-old wolf puppies spontaneously responding to social-communicative behaviors from an unfamiliar person by retrieving a ball. This behavioral expression in wolves has significant implications for our understanding and expectations of the genetic foundations of dog behavior. Importantly, our observations indicate that behavioral responses to human social-communicative cues are not unique to dogs. This suggests that, although probably rare, standing variation in the expression of human-directed behavior in ancestral populations could have been an important target for early selective pressures exerted during dog domestication.
|
|
| 10. |
- Wheat, Christina Hansen, et al.
(författare)
-
Wolf (Canis lupus) Hybrids Highlight the Importance of Human-Directed Play Behavior During Domestication of Dogs (Canis familiaris)
- 2018
-
Ingår i: Journal of comparative psychology (1983). - : American Psychological Association (APA). - 0735-7036 .- 1939-2087. ; 132:4, s. 373-381
-
Tidskriftsartikel (refereegranskat)abstract
- The domestication of animals and plants offers an exceptional opportunity to study evolutionary adaptations. In particular, domesticated animals display several behavioral alterations, including increased sociability and decreased fearfulness and aggression, when compared with their wild ancestors. However, studies quantifying simultaneous changes in multiple behaviors during domestication are lacking. Moreover, the role of human-directed play behavior has been largely neglected when studying the domestication process. Here we address these issues by examining behavioral changes during the domestication of the dog (Canis familiaris) from the gray wolf (Canis lupus) using a standardized behavioral test applied to wolf hybrids and several dog breeds. Contrary to expectations, our study provides little support for collective behavioral alterations. Specifically, although we found that wolf hybrids were less playful and overall more fearful than dogs, we did not detect any differences in sociability or aggression between wolf hybrids and dog breeds. Instead, our results suggest that behavioral alterations during domestication do not necessarily occur in concert and point to an important, but previously overlooked, role of selection on play behavior directed at humans during the domestication of dogs.
|
|
