Broodcare helpers in the cichlid fish Lamprologus brichardi: Their costs and benefits

‘Helping’ in birds and mammals involves seemingly altruistic behaviour. In the cichlid fish Lamprologus birchardi helpers are usually young of former broods staying in their parents' territories and participating in all kinds of parental duties (Broodcare, territory maintenance and defence). The discovery of helpers in fish offered the chance of attempting an extensive analysis of potential costs and benefits influencing the evolution of helpers in a vertebrate. Three factors proved to be of major importance in the cost-benefit analysis of helping as opposed to leaving for family-independent nonreproductive aggregations. Due to investment and to their rank within a family's hierarchy, helpers grow at a slower rate than non-helpers. This cost is compensated for by (i) a lower mortality risk to helpers caused by their access to a defended shelter and by protection afforded by bigger family members, and (ii) a positive contribution by helpers to the future reproductive success of their parents: females with helpers produce bigger clutches and consequently more free-swimming fry (=siblings). Other variables, such as the helpers' influence on the relative breeding success of their parents, broodcare experience through helping, the chances of territory take-over, parasitism of parents' reproduction and cannibalism are of minor importance. Similar social organizations in other fish are discussed with respect to their ecology and are compared with cooperatively breeding birds and mammals.     

Mating system of the Amazonian cichlid angel fish, Pterophyllum scalare.

The species, Pterophyllum scalare distinguishes itself by its breeding behavior, involving competition for territory, sexual partners, courtship and parental care. The purpose of this study was to identify the mating system adopted by this species of fish. Twenty males and twenty females were observed under semi-natural and experimental conditions to test the hypothesis of serial monogamy. Under semi-natural conditions, after the third breeding cycle, the couples changed mates. Under experimental conditions, the couples changed partners after the first breeding cycle. Under experimental conditions, mate recognition was investigated through the preference of the females, indicated by the time they spent with the males. The females were available or not for courtship from new males, depending on their aggressiveness or submission. The larger and more aggressive males obtained new mating opportunities while the submissive males were rejected by the females. The mated fish were aggressive towards intruders in the presence of the mate, protecting their pair bond. In the interval between breeding cycles, the couples did not display aggression towards intruders, confirming the hypothesis of serial monogamy. Best mate selection by the females and the opportunity of new matings for both sexes influenced the reproductive success of this species.     

Reproductive success and survivorship of the Galapagos Hawk Buteo galapagoensis: potential costs and benefits of cooperative polyandry

The Galapagos Hawk Buteo galapagoensis is one of few species showing cooperative polyandry. As many as four males may mate with one female and share a territory and nest, Such groups, on average, produce more young than monogamous pairs, but on a per male basis (assuming that each male of a group has an equal chance to fertilize each young) polyandrous males produce fewer young per year than monogamous males. Territorial breeding birds show higher yearly survivorship (90%) than non-territorial, non-breeding birds (50% or less). All territorial birds seem to remain on their territories for life, and monogamous pairs actually constitute the remnants of polyandrous groups. Some potential factors producing such an unusual system are discussed. Limited breeding space and high mortality among non-territorial birds seem to work in favour of group breeding in this and other cooperative species. Polyandry may be favoured because of the reduced value of extra females in hawk breeding behaviour. Equal-status males may occur because of the lack of kinship among cooperating males and the high potential genetic cost of being a helper in a long-lived, low fecundity species. Other possible factors favouring group breeding are territory acquisition and the variable nature of the Galapagos climate.     

Reproductive skew, costs, and benefits of cooperative breeding in female wood mice (Apodemus sylvaticus)

Two current models seek to explain reproduction of subordinatesin social groups: incentives given by dominants for peacefullyremaining in the group (reproductive skew model) or incompletecontrol by dominants. These models make different predictionsconcerning genetic relatedness between individuals for thedistribution of reproduction and the stability of cooperativebreeding associations. To test these models and to furtherexplore the relationships between reproductive skew, geneticrelatedness, and investment of each participant, we performedbehavioral observations of female wood mice (Apodemus sylvaticus)raising pups communally. Our results do not support previousmodels. Differences in lifetime reproductive success were significantlygreater within mother—daughter pairs than within pairsof sisters or unrelated females. Subordinate females of eitherbreeding unit did not differ in their direct reproduction.Calculations of inclusive fitness based on our results leadto the following predictions: (1) Communal nests should occuronly when ecological circumstances prevent solitary breeding.(2) Subordinate females gain the highest inclusive fitnessjoining their mothers; they also show the highest nursing investment.(3) Mothers should accept daughters, who have no opportunityfor solitary breeding. (4) Dominant sisters and unrelated femalesshould reject subordinate females because cooperative breedingreduces their reproductive success. However, breeding unitsof dominant sisters and unrelated females nevertheless occurand can be explained by our finding that such females significantlyreduce nursing time, which may help them save energy for futurebreeding cycles. Our data demonstrate that both genetic relatednessand investment skew are important in the complex evolutionof reproductive skew in cooperative breeding.     

Facultative schooling behavior in the spottail shiner (Notropis hudsonius): possible costs and benefits

Synopsis If an individual is less susceptible to predation in a group it should be able to reduce its vigilance for predators and perhaps also its tendency to flee from predators, thereby gaining time and energy for feeding and other activities. These predictions were examined in the field (Veronica Lake, northwestern Ontario) using a facultative schooling species, the spottail shiner (Notropis hudsonius). Schools of various sizes attacked with a fish predator model had a significantly lower reaction distance to the predator than solitary shiners. Solitary shiners must therefore invest more time and energy in defense but may gain a feeding advantage because their visual field does not overlap with conspecific competitors.     

Artificial weaning of calves: benefits and costs

Evidence indicates that allowing beef calves to stay in the maternal herd beyond the age of natural weaning promotes animal welfare and may enhance the cows' natural reproductive potential.     

Mating in aphidophagous ladybirds: costs and benefits

Abstract:  Mating costs and benefits were studied in three aphidophagous ladybirds, viz. Cheilomenes sexmaculata , Coccinella septempunctata and Propylea dissecta by subjecting them to different numbers of matings. Longevity, fecundity and percent egg viability were regressed with number of matings to determine the costs and trade-offs, if any. Longevity decreased with increasing number of matings in both C. sexmaculata and P. dissecta indicating a cost of mating. The lack of such a cost in C. septempunctata has been ascribed to spermatophore consumption by females of this ladybird. Both fecundity and percent egg viability increased with increasing number of matings and are probably indicative of the benefits. Short-lived females distributed their reproduction uniformly in their lifetime while long-lived females showed a high burst of reproductive activity followed by a gradual decline. Percent egg viability decreased after the completion of the requisite number of matings.     

Tidal cycling and parental behavior of the cichlid fish,Biotodoma cupido

Synopsis Parental behavior of the substrate-brooding cichlid, Biotodoma cupido, was studied in a small creek entering the lower Essequibo River, Guyana, where the freshwaters are affected by semi-diurnal tides. Physico-chemical variables of the tidal cycle were associated with the parental behavior of B. cupido. During late ebb and early flood tides, while off-spring were nest dependent, parents displayed intense aggression toward brood predators, mainly characins. At low tide, when the concentration of dissolved oxygen decreased to about 4 mg 1^–1 and that of free carbon dioxide increased to 28 mg 1^–1, parents entered a state of somnolence and brood predators vanished. Early flood tide brought an immediate and dramatic reversal of hypoxic and hypercarbic conditions and an associated renewal of aggressive and predatory activity. At very low tide, parents orally transferred the brood to a secondary nest depression in deeper water. The significance of water-level fluctuation to the evolution of this behavior, as well as that of parent-brood itineracy and the related phenomena of oral incubation and movable nests, is discussed.     

The costs and benefits of kin

Human Nature - In this paper data from a Tanzanian horticultural population are used to assess whether mother’s kin network size predicts several measures of children’s health and...     

Larval cannibalism in aphidophagous ladybirds: Influencing factors, benefits and costs

Spray retention on scentless chamomile and round-leaved mallow was characterized in relation to droplet size and travel speed. The effect of varying retention on biocontrol efficacy was studied using Colletotrichum truncatum and Colletotrichum gloeosporioides f. sp. malvae, the bioherbicide agents for the two weeds, respectively. In retention studies, a tracer dye solution was applied using a cabinet sprayer fitted with a fine, medium, or coarse nozzle at travel speeds of 0.5, 1.0, and 2.0 km/h that resulted in approximate application volumes of 500–2000 L/ha. Retention efficiency, a ratio between the volume retained on plants and actual volume applied, was calculated for each application. In general, finer sprays achieved higher retention efficiency on whole plants of both weeds. On an average, fine sprays resulted in 68% greater retention than coarse sprays on scentless chamomile and 22–59% on round-leaved mallow. Faster travel speeds increased spray retention only slightly. Applying the biocontrol agents at 500 L/ha with different droplet sizes showed different effects on weed control on scentless chamomile and round-leaved mallow. C. truncatum applied with fine droplets was more efficacious than treatments with coarser droplets on scentless chamomile. On round-leaved mallow, however, the efficacy of C. gloeosporioides f. sp. malvae did not appear to be substantially affected by the droplet size. This varying effect may be due to reduced retention on the vertical stems of round-leaved mallow, which is critical to biocontrol of this weed by C. gloeosporioides f.sp. malvae.     

Reproductive behavior of the Lake Malawi cichlid fish, <Emphasis Type="Italic">Tramitichromis intermedius</Emphasis>

Synopsis We studied the reproductive behavior of wild caught and captive-born, first generation offspring of the Lake Malawi fish, Tramitichromis intermedius(Teleostei, Cichlidae), held in aquaria. Spawning behavior includes an exchange of actions with dominant males performing bower construction and courtship behaviors while females focus on oviposition and mouthbrooding. Egg counts per oviposition and brooding and interbrooding periods of wild caught T. intermedius follow records of other mouthbrooding cichlid fishes. Observation of circling behavior suggests this behavioral trait may be used in mate choice as longer circling, indicating a secure territory and thus male dominance, leads to more oviposition events and hence the potential for larger broods. Comparisons of clutch size and total length of young at release from full-sized females vs. first spawners reveal smaller clutches and young from the younger females, most likely stemming from differences in body size. Investigation of spawning photoperiodicity also noted distinctions between the two groups with wild caught T. intermedius spawning activity peaking in the middle of the light cycle and captive-born, first spawners exhibiting no significant peak in activity. The trend to spawn midday is most likely influenced by predation factors, while the lack of a spawning periodicity in the offspring may be explained by developmental processes, the absence of environmental cues or the tendency for smaller males to be opportunistic in spawning events. The details of spawning behavior recorded in this study provide a database to investigate species differences and to indicate changes due to chemical and physical disturbances.     

Feeding behavior of the cichlid,Sarotherodon galilaeum: selective predation on Lake Kinneret zooplankton

In laboratory feeding trials, we analyzed the feeding behavior and selectivity of the cichlid, Sarotherodon galilaeum, for zooplankton prey from Lake Kinneret, Israel. The feeding behavior was dependent on fish size. Fish less than 20 mm SL fed on zooplankton as obligate particulate feeders. Fish from 20 to 42 mm SL fed either as particulate feeders or as filter feeders. Fish larger than 62 mm SL fed as obligate filter feeders. Particulate-feeding fish were size selective and had highest feeding electivities for large-sized zooplankton species. Filter-feeding fish had highest feeding electivities for zooplankton species with poor escape ability. In general, S. galilaeum predation pressure would be greatest on Ceriodaphnia reticulata, a large-bodied and easily captured species which is selected by both particulate-feeding and filter-feeding fish.