Developmental changes in the resting strategies of killer whale mothers and their calves in managed care from birth to 36 months

The development of cetacean sleep has not been explored fully. Questions such as whether cetacean mothers regulate their offspring’s resting behaviour and do resting behaviours change over the course of cetacean development remain unanswered. To address these questions, an investigation of the resting strategies and activity levels for four killer whale (Orcinus orca) calves and their mothers in managed care during free-swim conditions was conducted during the first three years of life. A series of interrelated hypotheses were assessed using three independent sets of archived data (24 h behaviour records, video recordings, and instantaneous sampling) collected from two facilities. Together, the results indicated that mothers adjusted their activity levels based on their calves’ current level of development. Floating, often a preferred resting behaviour, was rarely observed during the first post-parturition month for any of the mother–calf pairs. Rather, the mother–calf pairs tended to display fast-moving mother–calf swims with frequent trajectory changes as the calf gained swimming proficiency. Although floating occurred more frequently over time for all pairs, all four killer whale mother–calf pairs displayed a preference for a slower-paced pattern swim (i.e., swim-rest). Calves preferred to rest with their mothers over resting with others or independently. The similarities in resting strategies displayed by the killer whale mother–calf pairs housed in independent facilities without temporal overlap emphasizes the conserved nature and development of these strategies in a precocial cetacean species with extended maternal care.

Extended maternal care and offspring interactions in the subsocial Australian crab spider, Xysticus bimaculatus

Extended maternal care is considered a prerequisite for the evolution of permanent family grouping and eusociality in invertebrates. In spiders, the essential evolutionary transitions to permanent sociality along this ‘subsocial route’ include the extension of care beyond hatching, the persistence of offspring groups to maturation and the elimination of premating dispersal. Subsocial Australian crab spiders (Thomisidae) present a suitable system to identify the selective agents prolonging group cohesion. Particularly, the recent discovery of independently evolved subsociality in the thomisid Xysticus bimaculatus provides new potential for comparative studies to expand the limited understanding of group cohesion beyond the offspring’s potential independence and despite socially exploitative behaviour. Providing fundamental knowledge, the present study investigated maternal care and offspring interactions in X. bimaculatus for the first time. Nest dissections revealed that mothers produce exceptionally small clutches, potentially reflecting a limit in the number of juveniles they can successfully care for. A laboratory experiment demonstrated crucial benefits for offspring in receiving maternal care beyond nutritional independence, mediated by extensive maternal food provisioning. However, prey-sharing also occurred between juveniles irrespective of maternal presence, which marks this species’ predisposition for exploitative feeding behaviour. I therefore suggest X. bimaculatus as a suitable model for investigating the regulation of communal feeding in group-living spiders.

Whipspiders (Arachnida: Amblypygi) in amber from the Early Eocene and mid-Cretaceous, including maternal care

Two new genera and species of fossil whipspiders (Chelicerata: Arachnida: Amblypygi) are described from Tertiary and Cretaceous ambers of southern Asia. Paracharonopsis cambayensis Engel & Grimaldi, new genus and species, preserved in Cambay amber of Ypresian age from western India is the first Tertiary and Asian fossil of the Paleoamblypygi, a highly relict taxon that includes the Late Carboniferous genus Graeophonus Scudder and the living West African species Paracharon caecus Hansen. Paracharonopsis cambayensis is one of the few examples in Cambay amber of a biotic connection to Africa; most taxa show widespread or Laurasian distributions. Kronocharon prendinii Engel & Grimaldi, new genus and species, is the first Cretaceous amber whipspider and putatively a sister group to the Phrynoidea (= Apulvillata). The holotype female of K. prendinii is preserved with the remains of three nymphs near her, documenting the Early Cretaceous presence of the extended maternal care so distinctive for the order, and a behavioral repertoire widespread among arachnids.

Maternal Food-Supply Activity and Its Regulation in Coelotes Terrestris (Araneae, Agelenidae)

The funnel-web spider Coelotes terrestris (Agelenidae) displays extended maternal care, especially characterized by a progressive provisioning of the young during a four-eight week gregarious phase. As they grow up, the spiderlings are provided with a increasing amount of prey, which is captured on the web and carried by the mother into the silk tube that represents the nest. This paper is aimed to determine the mechanism that could regulate, throughout the gregarious phase, this food-supply activity. Eleven females were observed, at different times, from one week before egg-laying till one week after the progeny's dispersal. Females' feeding behaviour noticeably changed from the young's emergence onwards. In particular, the prey was less and less handled and the overall time during which the mother kept her prey for herself-Prey Handling Time (PHT)-steadily decreased. Meanwhile, the spiderlings reacted more and more rapidly to the mother's prey catching and carrying, and they stimulated her more and more actively. The mother's prey-supply behaviour was experimentally shown to be modifiable within a short delay. Separating the mother from her brood made her shift her "Prey Handling Time" from a few minutes to more than two hours (i. e. about the level of the pre-emergence PHT). Conversely, reuniting the mother with her brood lead to an equivalent decrease of the PHT. This phenomenon was obtained at four different periods during the gregarious phase. The present study shows that, in this invertebrates species, the maternal provisioning activity is essentially regulated by exogenous factors: i. e. stimulations (that qualitatively and quantitatively variate in the course of time) emanating from the developing progeny.