A high level of nest predation observed in a large Sand Martin (Riparia riparia) colony

During the 2016 field season, we investigated the influence of intense nest digging predation at a Sand Martin colony that is situated in natural habitat along the Tisza river. Over this season, foxes dug a large number of holes which either partly or fully destroyed 39% of burrows in a large colony, comprising over 1,500 pairs. This high level of predation caused death and/or injury to between 7% and 44% of breeding individuals and lowered the reproductive success of the colony as on average 20% (between 5% and 43%) less nestlings were fledged. The level of digging showed a negative exponential growth with burrow density. Our observations show that the burrows were most at threat between 0 m and 0.4 m from the top and between 0 m and 1.4 m from the bottom of the wall. These observations show that it is critically important to decrease the number of foxes and other potential nest predators, whose numbers have increased well above ‘natural’ levels over the last decade, in regions where Sand Martins are nesting as this species is in drastic decline.

Flight and Digging Effort in Leaf-cutting Ant Males and Gynes

The nuptial flight and nest digging are high intensity activities which consume body reserves. The flight and digging effort was quantified by measuring the carbohydrate and total lipids content in males and females before and after the nuptial flight, and the queen’s digging effort during the foundation. The digging effort was quantified by experimentally stimulating the queens to dig a nest – one, two or three consecutive times – compared to the queens that did not dig. The colorimetric method was used to determine the soluble carbohydrates and extraction method of immersion was used to determine the total lipids. The results showed significant loss of carbohydrates and total lipids in males and females after the flight. On average the males contained 0.027 mg of soluble carbohydrates before the nuptial flight, and 0.005 mg after the nuptial flight, and the females contained 0.129 mg of soluble carbohydrates before the nuptial flight, and 0.079 mg after the nuptial flight. For the males the percentage of lipids decreased from 5.27±1.07% to 2.60±0.63% and for females from 36.46±4.86% to 32.62% after the nuptial flight. The digging effort of the queen caused a slight reduction in total carbohydrates, it was without digging 0.054 mg, normal digging 0.055 mg, double digging 0.045 mg (decrease of 20,22 %), and triple digging 0.044 mg (decrease of 20 %) per queen. Based on our results we conclude that the carbohydrate content is the main energetic resource used for the nuptial flight and nest digging, for males and gynes of leaf-cutting ants.

Nest Digging by Leaf-Cutting Ants: Effect of Group Size and Functional Structures

Leaf-cutting ant workers dig underground chambers, for housing their symbiotic fungus, interconnected by a vast quantity of tunnels whose function is to permit the entrance of food (leaves), gaseous exchanges, and movement of workers, offspring, and the queen. Digging is a task executed by a group of workers, but little is known about the group effect and group-constructed functional structures. Thus, we analyzed the structures formed by worker groups (5, 10, 20, and 40 individuals) of the leaf-cutting ant,Atta sexdens rubropilosa, for 2 days of excavation. The digging arena was the same for the 4 groups, with each group corresponding to a different density. Our results verified a pattern of tunneling by the workers, but no chamber was constructed. The group effect is well known, since the 40-worker group dug significantly more than the groups of 5, 10, and 20. These groups did not differ statistically from each other. Analysis of load/worker verified that workers of the smallest group carried the greatest load. Our paper demonstrates the group effect on the digging of nests, namely, that excavation is proportional to group size, but without emergence of a functional structure such as a chamber.

Spawning sockeye salmon fossils in Pleistocene lake beds of Skokomish Valley, Washington

An assemblage of fossil sockeye salmon was discovered in Pleistocene lake sediments along the South Fork Skokomish River, Olympic Peninsula, Washington. The fossils were abundant near the head of a former glacial lake at 115 m elevation. Large adult salmon are concentrated in a sequence of death assemblages that include individuals with enlarged breeding teeth and worn caudal fins indicating migration, nest digging, and spawning prior to death. The specimens were 4 yr old and 45–70 cm in total length, similar in size to modern sockeye salmon, not landlocked kokanee. The fossils possess most of the characteristics of sockeye salmon, Oncorhynchus nerka, but with several minor traits suggestive of pink salmon, O. gorbuscha. This suggests the degree of divergence of these species at about 1 million yr ago, when geological evidence indicates the salmon were deposited at the head of a proglacial lake impounded by the Salmon Springs advance of the Puget lobe ice sheet. Surficial geology and topography record a complicated history of glacial damming and river diversion that implies incision of the modern gorge of the South Fork Skokomish River after deposition of the fossil-bearing sediments.

Courtship and spawning competition in pink salmon (Oncorhynchus gorbuscha)

Male pink salmon cluster in groups of up to 10 or more around a female as she prepares the substrate for spawning. The largest male in the group (in length and dorsal hump development) stays closest to the female; the others maintain a size-related hierarchy behind the pair. Position in the group is determined by frequent aggressive interactions among the members. Often a relatively small "outlier" male holds position near the central pair, to one side of the nest. These males are "female-like" in colour and size, and the dorsal hump is small. When the primary male settles into the nest bottom and quivers beside the female, males in the associated group, including the small outlier, dash into the nest. When the female and primary male spawn, some or all of the group males release sperm. Nest-digging females are territorial; they attack other females and small males. Their primary males are aggressive towards other males, but not towards females. They frequently attack the males closest to them in their group, but also attack nongroup males, including other large males who try, usually unsuccessfully, to replace them as the primary male. The phenomena of many males at a single nest, great variability in dorsal hump development, and outlier vs. fighting behaviour are all associated with male competition for access to spawning females.

Reproductive Behavior of Hybrid Charr (Salvelinus fontinalis × S. namaycush)

Observations of the reproductive behavior of splake (Salvelinus fontinalis × S. namaycush) planted in Jack Lake, Algonquin Park, Ont., indicated that they spawned on rocky shoals from late October to early November. In mid-October, splake approached the spawning locations. By late October females had selected redd sites and dominant males were aggressively defending the sites that had been cleared by the females, against other males. Redd digging was variable in duration and frequency. Depth of water over redds varied between 0.5 and 4 m. No attempts were made to cover the eggs, most of which settled into the crevices between rocks. Males and females used acoustic signals during both aggression and courtship. The male initiated courtship by maintaining his head over the female's tail, then crisscrossing over the tail. Parallel positioning of the two sexes was a prerequisite to release of sex products. Visual and sonic cues appeared to be used in sequencing behavior. Circling functioned as a neutral action to which any other courting behavior could revert. Nest digging ceased after completion of egg deposition. A swim-in-place behavior of the female was a positive indicator of egg deposition. Egg predation by adult splake was observed, but it appeared to offer no serious threat to natural reproduction. Laboratory observations of splake reproductive behavior in aquaria did not indicate any behavioral obstacles to successful natural reproduction. Courtship behavior and egg deposition in the artificial spawning beds was followed by normal development and emergence of fry.Key words: splake, reproductive behavior, Ontario, visual and acoustic signaling

Behavior of the hunting wasp Liris nigra V.d.L. (Hymenoptera, Larrinae) in particular or in unusual situations

On the average, a typical nesting cycle of this cricket-hunting wasp involves the following sequence of activities: nest digging—prey hunting and stinging (four stings are usually given)—malaxation of foreleg(s)—storage in nest—malaxation again, in nest—egg laying—nest closure.Many variations and unusual outcomes were observed, some mainly at particular stages of the life or nesting cycle of the wasp: nesting cycles with missing last stage(s) (early period of reproductive season and of daily cycle); abortive individual activities discontinued before completion (early stages of successive phases of nesting cycle); condensed nesting cycles, based on use of paralyzed crickets, nests of other Liris wasps (end of reproductive season).Other unusual behavior was observed in unusual situations or in case of interference. Various patchworks of response components were often performed, particularly in ambivalent or ambiguous contexts.Discussion of these unusual outcomes points to the possible importance of response, posture, and stimulus components or objects common to several nesting activities; of displacement activities; of changes in responsiveness of the wasp; and of stimulus situations that can vary in graded rather than discrete fashion.