Hans Temrin

Singing behaviour in relation to polyterritorial polygyny in the wood warbler (phylloscopus sibilatrix)

Abstract Male wood warblers ( Phylloscopus sibilatrix ) decreased singing activity after pairing. A few days later they began to sing intensively again, but only in a secondary territory or in an outlying part of the primary territory. The long song characteristic of unpaired males was replaced by a short song after pairing. When singing at a distance from the nest, paired males changed to the long song. It is suggested that song in the wood warbler is important for female attraction and that the singing behaviour found in the studied wood warblers clearly indicates that all paired males tried to attract a second female.

Polyterritorialitytion in passerine birds

In some birds, males defend two spatially separated territories and attract females to each one in turn. it has been proposed that this behaviour, referred to as polyterritoriality, allows males to conceal their marital status, thereby deceiving females into accepting polygyny against their best interests. The deception hypothesis has gained general acceptance as an explanation for polyterritoriality in birds, but until recently the empirical basis for the hypothesis rested almost entirely on studies of Swedish populations of the pied flycatcher (Ficedula hypoleuca). New findings, emerging from further studies of the pied flycatcher and of other species, suggest several alternative selection pressures that may have favoured polyterritoriality.

Female pairing options in polyterritorial wood warblers Phylloscopus sibilatrix: are females deceived?

Abstract Polyterritoriality has been explained as a way in which paired males hide the fact that they are already paired, in order to attract additional females. The deception hypothesis suggests that females choosing already-paired males in secondary territories are less successful than if they had chosen unpaired males available at that time. Lack of time for females to assess a males pairing status has been suggested as the constraint making ‘deception’ possible. In this study of polyterritorial wood warblers, the actual options available for a female who chose an already-paired male were investigated. There were differences in the behaviour of males trying to attract females: paired males left their secondary territories more often than unpaired males left their territories. This could make it possible for females to assess a males pairing status. Since pairing status seems possible to detect at an early stage, lack of time is not likely to constrain the females opportunity to detect deception. When females were attracted to already-paired males, the unpaired males available often occupied territories where wood warblers rarely bred. This, and the fact that these females had a similar, or even greater, short-term fledging success than those who later paired with the unpaired males they had rejected, suggests that females may be adopting the best mating option available at a given time.

Are Stepchildren Over-Represented as Victims of Lethal Parental Violence in Sweden?

Evolutionary psychologists have suggested that stepchildren should be over–represented as victims of lethal parental violence compared with children living with their two genetic parents, because of relatively more lapses in parental solicitude among step–parents. In our study, using data over a period of 35 years in Sweden (1965–1999), there was no overall over–representation of stepchildren as victims. For very young stepchildren there was a tendency for over–representation. In families with both stepchildren and children genetically related to the offender, genetic children tended to be more likely to be victims.

Parental investment in monogamous pairs of Wood Warblers (Phylloscopus sibilatrix)

In Wood WarblersPhylloscopus sibilatrix in South-Central Sweden, paired males spend considerable time trying to attract additional females either in outlying parts of their territory or in a secondary territory at some distance from the first. Approximately 20 % of the paired males succeed in attracting an additional female, while the rest stay monogamous. When the eggs hatch males assist in feeding the young. We studied parental care in monogamous pairs and investigated the proportion of males being paired in relation to the hatching of broods. Both feeding frequency and load size increased with age of the young. Feeding frequencies were higher in males than in females, while there was no difference in load size between the sexes. Nestlings are unable to thermoregulate the first days after hatching, and females spent considerable time brooding them. We also show that males do not gain by deserting the family when the broods hatch, since the probability to attract additional females at that time is low. In einer Population Südschwedens wendeten die Männchen des Waldlaubsängers erhebliche Zeit auf, um entweder in entfernten Teilen ihres Reviers oder in einem zweiten Revier in einiger Entfernung weitere Weibchen anzulocken. Etwa 20 % der Männchen konnte so ein zweites Weibchen an sich binden, die übrigen blieben monogam. Nach dem Schlüpfen halfen die Männchen bei der Jungenfütterung. Die Brutpflege bei monogamen Paaren wurde untersucht, ebenso das Verhältnis der verpaarten Männchen zu geschlüpften Bruten. Fütterfrequenz und Größe einer Futterportion nahmen mit dem Wachstum der Jungen zu. Bei den Männchen war die Fütterfrequenz höher als bei den Weibchen, nicht jedoch die Größe einer Futterportion. Da die Nestlinge während der ersten Tage ihre Körpertemperatur nicht aufrecht erhalten können, werden sie vom Weibchen ausdauernd gehudert. Männchen gewinnen nichts, wenn sie die Familie nach dem Schlüpfen der Jungen verlassen, da die Wahrscheinlichkeit, ein neues Weibchen zu finden, in dieser Zeit gering ist.

How reliable are behavioral cues for assessment of male mating status in polyterritorial wood warblers, Phylloscopus sibilatrix?

It has been suggested that polyterritoriality in birds, i.e. mated males defending two spatially separated territories, deceives females into accepting polygyny against their best interest. Mated males singing on secondary territories should make it difficult for new arriving females to assess the mating status of unmated and mated males advertising to females. However, there have been objections to the deception hypothesis, suggesting that differences in territorial behavior between males of different mating status may make correct assessment possible. Polyterritorial males frequently leave their secondary territory to visit the female in the primary territory, thereby revealing their mating status to females in search of mates. The aim of this study is to investigate how reliable behavioral cues are in assessing the mating status of males in polyterritorial wood warblers. Our study shows that singing activity of mated males on secondary territories and unmated males was similar in the morning, while there was a significant difference in the afternoon. Unmated males spent, on average, more time on their territories than mated males spent on their secondary territories. However, there was considerable variation in both unmated and mated males in the frequency in which they left their territories. For instance, unmated males left their territories quite frequently early in the season compared to later. Hence, females must be able to interpret singing behavior and a male leaving his territory differently depending on time of the season and time of the day in order to correctly assess the mating status of advertising males. Estimating the increase in probability of finding an unmated male by using behavioral cues showed that females could increase the probability of finding an unmated male compared to random choice with respect to mating status. The uncertainty was, however, still considerable. The most important factor affecting the probability of finding an unmated male was the proportion of mated males on secondary territories compared to unmated males. Our study suggests that presence on a territory is not a reliable cue for the assessment of male mating status in polyterritorial wood warblers.

Training pair-housed Rhesus macaques (Macaca mulatta) using a combination of negative and positive reinforcement.

When training animals, time is sometimes a limiting factor hampering the use of positive reinforcement training (PRT) exclusively. The aim of this study was to evaluate the effects of a combination of negative and positive reinforcement training (NPRT). Twenty naïve female Rhesus macaques (Macaca mulatta) were trained in 30 sessions with either PRT (n=8) or NPRT (n=12) to respond to a signal, move into a selected cage section and accept confinement. In the NPRT-group a signal preceded the presentation of one or several novel, and thus aversive, stimuli. When the correct behaviour was performed, the novel stimulus was removed and treats were given. As the animal learned to perform the correct behaviour, the use of novel stimuli was decreased and finally phased out completely. None of the PRT-trained animals finished the task. Ten out of 12 monkeys in the NPRT-group succeeded to perform the task within the 30 training sessions, a significant difference from the PRT-group (p=0.0007). A modified approach test showed no significant difference between the groups (p=0.67) in how they reacted to the trainer. The results from this study suggest that carefully conducted NPRT can be an alternative training method to consider, especially when under a time constraint.

Dogs, but not wolves, lose their sensitivity towards novelty with age

Selection on behavioural traits holds a prominent role in the domestication of animals. Specifically, a reduction of the fear response is considered a key component, with domesticated animals expressing lower levels of fear towards novelty than their wild counterparts. Previous work has suggested that this is caused by a delay in the onset of fearful behaviour during early ontogeny in domesticated canids. However, it remains unclear how the developmental timing of initial fear expression affects fearfulness later in development. Here we present the first extended examination of the development of fear behaviour in wolves and dogs, using repeated novel object tests between six and 26 weeks of age. Contrary to expectations, fear of novelty did not change in wolves with age, but dogs expressed decreased latency to approach a novel object with age, resulting in a species difference at the end of the measured period. Our results thereby suggest that 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 differences in fear expression between wolves and dogs are caused by a loss of sensitivity towards novelty with age in dogs.

Wolf (Canis lupus) hybrids highlight the importance of human-directed play behavior during domestication of dogs (Canis familiaris).

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.

Reproductive success and parental effort of females in polyterritorial wood warblers Phylloscopus sibilatrix: The influence of nest predation

Abstract:The polygyny threshold model explains that female choice of already-mated males should be selected for when mated males have resources that compensate for the cost associated with sharing ...