Parthenogenesis is a natural form of asexual reproduction in which embryos develop in the absence of fertilisation. Most commonly found in plants and invertebrate organisms, an increasing number of vertebrate species have recently been reported employing this reproductive strategy. Here we use DNA genotyping to report the first demonstration of an intra-individual switch from sexual to parthenogenetic reproduction in a shark species, the zebra shark Stegostoma fasciatum. A co-housed, sexually produced daughter zebra shark also commenced parthenogenetic reproduction at the onset of maturity without any prior mating. The demonstration of parthenogenesis in these two conspecific individuals with different sexual histories provides further support that elasmobranch fishes may flexibly adapt their reproductive strategy to environmental circumstances.

The purpose of this study was to enrich parrot enclosures by creating foraging opportunities appropriate for the species and to investigate the possible preference for a variable versus a constant food supply. The foraging device comprised of a length of wood (2×0.08×0.08m) with 50 holes (0.02m diameter x 0,02m depth) drilled into one face. Food was placed in the holes of the foraging device in one of two distributions: ‘constant’, one food item in every hole (total = 50 food items) or ‘variable’, 5 food items in 10 of the holes (total = 50 food items). The holes were then covered with starch paper. During the enrichment period the parrots spent significantly more time allopreening than in the baseline or post-enrichment periods. The results also provide some evidence of contrafreeloading in parrots, but no preference for a variable over a constant food source. The study shows that providing extra foraging opportunities for parrots is a useful form of enrichment.

Scientific Reports 7: Article number: 40537; published online: 16 January 2017; updated: 07 April 2017. This Article contains errors in Table 1. The correct Table 1 appears below as Table 1.