All day-long: Sticklebacks effectively forage on whitefish eggs during all light conditions

The three-spined stickleback Gasterosteus aculeatus invaded Lake Contance in the 1940s and expanded in large numbers from an exclusively shoreline habitat into the pelagic zone in 2012. Stickleback abundance is very high in the pelagic zone in winter near the spawning time of pelagic whitefish Coregonus wartmanni, and it is hypothesized that this is triggered by the opportunity to consume whitefish eggs. Field sampling has qualitatively confirmed predation of whitefish eggs by stickleback, but quantification has proven difficult due to stormy conditions that limit sampling. One fundamental unknown is if freshwater stickleback, known as visual feeders, can successfully find and eat whitefish eggs during twilight and night when whitefish spawn. It is also unknown how long eggs can be identified in stomachs following ingestion, which could limit efforts to quantify egg predation through stomach content analysis. To answer these questions, 144 individuals were given the opportunity to feed on whitefish roe under daylight, twilight, and darkness in controlled conditions. The results showed that stickleback can ingest as many as 100 whitefish eggs under any light conditions, and some individuals even consumed maximum numbers in complete darkness. Furthermore, eggs could be unambiguously identified in the stomach 24 hours after consumption. Whitefish eggs have 28% more energy content than the main diet of sticklebacks (zooplankton) based on bomb-calorimetric measurements, underlining the potential benefits of consuming eggs. Based on experimental results and estimates of stickleback abundance and total egg production, stickleback could potentially consume substantial proportions of the total eggs produced even if relatively few sticklebacks consume eggs. Given the evidence that stickleback can feed on eggs during nighttime spawning and may thereby hamper recruitment, future studies aimed at quantifying actual egg predation and resulting effects on the whitefish population are urgently needed.

The remarkable biology of a new species of Gelis Thunberg, 1827 (Ichneumonidae, Phygadeuontinae), a solitary endoparasitoid of fresh eggs of Timarcha (Coleoptera, Chrysomelidae)

A new species, Gelis timarchae Schwarz, Shaw & Kan, is figured and described from specimens reared as a solitary endoparasitoid of fresh eggs of Timarcha nicaeensis in the south of France. Oviposition behaviour of the adult parasitoid, directly into the host cytoplasm, is described and links to videos are given. This appears to be the first record of any ichneumonid developing as an endoparasitoid of an insect egg, and it is a major departure from hitherto known ectoparasitoid (or spiders’ egg-predation) behaviour in the genus Gelis. Fluid from the host egg issuing from the base of the parasitoid’s ovipositor early in the oviposition process is interpreted as a necessary reduction of hydrostatic pressure before the parasitoid egg can be forced down the ovipositor. The egg and first instar larva are figured; the latter is caudate, with the caudal appendage very unusual in being bifurcate. The complex phenology and diapause of the parasitoid were investigated partly experimentally; it is broadly bivoltine with a prepupal diapause in summer, but extra generations and prolonged diapause were both also seen.

Fore reef location influences spawning success and egg predation in lek-like mating territories of the bird wrasse, Gomphosus varius

Many fish spawn in aggregations, but little is understood about the dynamics governing the success of spawning interactions. Here, we evaluate the influence that location of lek-like mating territories has on spawning interactions of Gomphosus varius. We used direct observations of spawning and egg predation events as well as local population counts to compare the rates of spawning, spawning interruptions, and predation on the eggs of G. varius at Finger Reef, Apra Harbor, Guam. We hypothesized that spawning rates would be highest among seaward locations that facilitate transport of pelagic larvae from reefs and that those territories would subsequently experience higher densities of egg predators, egg predation rates, and spawning interruptions. Male spawning success was highly skewed by mating territory location, with holders of the outer, seaward mating territories being more successful than those males holding territories in the middle and inner areas of the aggregation site. Within the outer territories, male mating success was also skewed by location. Egg predation was observed occasionally and increased linearly with bird wrasse spawning frequency. The population densities of egg predators were distributed equally across the study area. Spawning interruptions occurred most frequently within the inner zone of the spawning aggregation due to greater male-male aggression in intraspecific competition for females and territories. This study provides evidence that reef location influences the spawning success, egg predation rates, and spawning interruption rates of fishes that reproduce using lek-like mating territories.

Oropendola nest predation and rodent consumption by the black-capped capuchin (Sapajus apella) in the Manu Biosphere Reserve, Peru

The Neotropical primate Sapajus apella (Linnaeus, 1758), the black-capped capuchin monkey, is widely distributed across the Amazon basin (Boubli et al., 2020). Capuchins are generalist platyrrhines, occurring in most tropical forest types, where they forage opportunistically (Sabbatini et al., 2008; Lynch Alfaro et al., 2012; Boubli et al., 2020). They exploit a diverse variety of food sources, such as fruit, seeds, arthropods and vertebrate prey including small mammals (Rose, 1997; Resende et al., 2003; Albuquerque et al., 2014). Their foraging strategy is highly resourceful and adaptive, and are often considered as important predators of nests (Canale and Bernardo, 2016), including those of caiman (Torralvo et al., 2017), coatis (Rose, 1997) and especially of birds (Watts, 2020). In this work, we report observations of a foraging event by Sapajus apella that includes the first record of egg predation of the russet-backed oropendola, Psarocolius angustifrons (von Spix, 1824), as well as the predation of arboreal rodents, Oecomys sp. (Thomas, 1906).

Ground cover presence in organic olive orchards affects the interaction of natural enemies against Prays oleae, promoting an effective egg predation

The olive moth, Prays oleae, is one of the most common insects that damages olives in the circum-Mediterranean region. The establishment of ground cover within olive orchards has been promoted in this region in recent years to avoid erosion and soil degradation. Nevertheless, its role as a shelter for natural enemies of pests has been controversial. In this study we have investigated the effectiveness of the biological control of P. oleae in organic olive orchards with ground cover (mowed) and without ground cover (tilled). For this (1) we assessed the relationship between predated eggs and the abundance of natural enemies in both types of orchards; (2) we compared both the potential damage of the pest and the egg hatching in the two types of orchards; and (3) we examined the interaction amongst families of natural enemies and P. oleae (as adults and as predated eggs). The results showed that there is a high rate of predation in the studied olive orchards, 81% of the eggs were predated, 12.2% hatched, and 6.9% were live eggs. However, mowed orchards were more effective for controlling P. oleae by means of egg predation rather than tilled orchards, i.e., in mowed orchards, whilst the potential damage of the pest was higher, egg hatching was rather low. The structure of the adult arthropod community, i.e., the composition and abundance of families of natural enemies did not differ between the orchards, but the abundance of the families Anthocoridae, Miridae and Scelionidae was significantly higher in the mowed orchards. Finally, the interaction amongst natural enemies and P. oleae showed that the families that better explained the effects on egg predation were Aeolothripidae, Anthocoridae, Miridae, Chrysopidae (predators), and Formicidae (omnivore). We discuss the results in terms of ecological interactions of trophic guilds and we conclude that the establishment and maintenance of ground cover in organic olive orchards, at least in June and July, is of great significance because it positively affects the egg predation of P. oleae. This effect is especially significant when there is a low abundance of natural enemies in the olive orchards.

PREDATION OF PALE-BREASTED THRUSH EGGS BY THE ARIEL TOUCAN IN BRAZIL: FAILURE OF THE ANTI-PREDATORY STRATEGY

The Channel-billed Toucan (Ramphastos vitellinus ariel) is an omnivorous bird that eventually is nest-robbers. Several birdsongs display anti-predatory strategies such as attacks and mobbing calls to face this kind of predators. This note reports a predatory event of one Channel-billed Toucan upon eggs of Pale-breasted Thrush (Turdus leucomelas), and describe the anti-predatory behavior, principally alert and mobbing calls of the thrush. Even though the Pale-breasted Thrush displayed the anti-predatory behaviors to harass the toucan, the egg predation was not avoided. Although the predation upon eggs by Ramphastos vitellinus has been reported several times, the majority of reports lacks of identity of the bird species affected, this being the first confirmed record in Turdus leucomelas.

Inferred predation of Fairy Tern eggs by Ruddy Turnstones at Rottnest Island, Western Australia, an internationally significant shorebird site

Ruddy Turnstones Arenaria interpres have been identified as egg-predators at seabird and shorebird colonies, including gull and tern colonies in the tropics and Northern Hemisphere. The Australian Fairy Tern Sternula nereis nereis is a threatened (Environment Protection and Biodiversity Conservation Act 1999: Vulnerable) coastal seabird, whose breeding behaviour and ecology expose it to a wide range of threats. This study describes inferred predation on Fairy Tern eggs at a small breeding colony on Rottnest Island, Western Australia, by Ruddy Turnstones, a previously unsuspected predator for thisspecies. Unlike the behavioural response shown towards Silver Gulls Larus novaehollandiae and Australian Ravens Corvus coronoides, which includes collective group defence and dive-bombing, Fairy Terns showed a lack of aggression towards Turnstones within the colony. The lack of a behavioural response suggests that the Terns did not recognise the Turnstones as predators, which may increase the risk of egg-predation. This study suggests that we should be alert to threats from unsuspected predators, which have the potential to reduce the breeding success of this Vulnerable tern.