Climate and body size influence nest survival in a fish with parental care

1. The current study examined the effect of broad-scale climate and individual-specific covariates on nest survival in smallmouth bass over a 20-year period. 2. Large-scale climate indices [winter North Atlantic Oscillation (NAO) and winter El Ni?o/Southern Oscillation (ENSO)] and body size of parental males were important covariates in nest survival along with nest age and a quadratic trend in survival. 3. We did not find an effect due to a habitat covariate (total effective fetch) or a phenology covariate (degree-days at start of nesting) on nest survival. 4. Male size in the second half of the nesting season was a more influential covariate on nest success than male size in the first half or throughout the nesting period. 5. We present evidence showing that winter NAO/ENSO indices establish limnological conditions the following spring that influence thermal stability of the lake during the nesting period. 6. The combined climate and body size covariates point to nest survival as a function of lagged climate-scale influences on limnology and the individual-scale influence of bioenergetics on the duration of parental care and nest success.     

Nest-site selection in a fish species with paternal care

Hydrobiologia - Fish that perform paternal care may increase their fitness by choosing nest sites that enhance survival and development of embryos. We studied nest-site choice with respect to...     

Pectoral fin size in a fish species with paternal care: a condition-dependent sexual trait revealing infection status

1. The three-spined stickleback, Gasterosteus aculeatus L., is a territorial fish with exclusive male parental care. Males oxygenate the eggs with fanning movements of their pectoral fins. The present authors investigated whether the apparent sexual differences in the functional demands of the pectoral fins have resulted in sexual differences in fin size. If males have relatively larger pectoral fins, females may use this as a signal to aid their mate choice for good fathers. Therefore, further objectives were to study the condition-dependency of relative pectoral fin size in males and the relationship with male parasite load. 2. Reproductively active males possessed relatively larger pectoral fins than females in both wild-caught and laboratory-bred fish. 3. In the field, caring males with relatively large pectoral fins were in better physical condition and had more food in their stomachs. 4. Relatively small pectoral fins and poor body condition were associated with infection by the intestinal parasite Pomphorhynchus laevis (Acanthocephala), the prevalent parasite species in the study population.     

Male size determines reproductive output in a paternal mouthbrooding fish

Size can have strong effects on reproductive success in both males and females, and in many species large individuals are preferred as mates. To estimate the potential benefits from mate choice for size in both sexes, I studied the effects of the size of each sex on the reproductive output of pairs of Banggai cardinalfish, Pterapogon kauderni, a sexually monomorphic obligate paternal mouthbrooder. When pairs were allowed to form freely, a size-assortative mating pattern was observed and larger pairs had a higher reproductive output as determined by total clutch weight and egg size. To separate the potential benefits from mate choice for size for each sex, I subsequently used these pairs to form reversed size-assortative pairs, that is, the largest male paired to the smallest female and vice versa. I found a positive correlation between male size and clutch size: relatively heavier clutches were found in pairs where females were given a larger male. This suggests that the size of the male influences clutch weight. For egg size, however, the size of both sexes seemed important. The study reveals the benefits of mutual mate choice on size in this species: larger females provide larger eggs and larger males can brood heavier clutches. Furthermore, these results suggest that females differentially allocate resources into the eggs according to the size of the mate.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

Isotocin regulates paternal care in a monogamous cichlid fish

While the survival value of paternal care is well understood, little is known about its physiological basis. Here we investigate the neuroendocrine contributions to paternal care in the monogamous cichlid, Amatitlania nigrofasciata. We first explored the dynamic range of paternal care in three experimental groups: biparental males (control fathers housed with their mate), single fathers (mate removed), or lone males (mate and offspring removed). We found that control males gradually increase paternal care over time, whereas single fathers increased care immediately after mate removal. Males with offspring present had lower levels of circulating 11-ketotestosterone (11-KT) yet still maintained aggressive displays toward brood predators. To determine what brain regions may contribute to paternal care, we quantified induction of the immediate early gene c-Fos, and found that single fathers have more c-Fos induction in the forebrain area Vv (putative lateral septum homologue), but not in the central pallium (area Dc). While overall preoptic area c-Fos induction was similar between groups, we found that parvocellular preoptic isotocin (IST) neurons in single fathers showed increased c-Fos induction, suggesting IST may facilitate the increase of paternal care after mate removal. To functionally test the role of IST in regulating paternal care, we treated biparental males with an IST receptor antagonist, which blocked paternal care. Our results indicate that isotocin plays a significant role in promoting paternal care, and more broadly suggest that the convergent evolution of paternal care across vertebrates may have recruited similar neuroendocrine mechanisms.     

Body size mediated effects of multiple abiotic stressors on the growth and social behaviour of an estuarine fish,Australian Bass (Macquaria novemaculeata)

Environmental Biology of Fishes - Anthropogenic climate change is expected to result in dramatic shifts in the abiotic conditions within estuaries, including an elevation of temperature and...     

Body size and shoaling in fish

Shoaling behaviour is generally described as a trade-off between the anti-predator benefits of living in groups and the costs of increased foraging competition. An individual's fitness varies as a function of shoal size and shoal composition, and this relationship is potentially body length dependent. As teleost fishes show indeterminate growth, many populations exhibit a broad range of individual body lengths. The latter is used as a criterion in active choice of shoaling companions, and shoals are often size-assorted. This reduces predation risk through minimizing phenotypic oddity, and may reduce competition between size-classes. There is some evidence for a positive relationship between shoal size and the body length of shoal members, although it remains unclear whether this is a result of active shoal-size choice or a by-product of the body length distribution of the population. Shoal membership is highly dynamic and individuals may maximize their fitness by switching frequently between groups of varying size and composition in response to changes in their physiological stage and the external environment. Fish shoals provide an excellent opportunity to investigate the functions and mechanisms of group living, and future studies should aim to take an integrated view of individual behaviours, group size and phenotypic composition when investigating group choice decisions.     

Seasonal sex role changes in the blenniid Petroscirtes breviceps, a nest brooder with paternal care

The plasticity of the sex roles in the blenniid fish Petroscirtes breviceps , a nest brooder with exclusive paternal care, was studied throughout an 8 month breeding season. Males performed most courtships early and late in the breeding season, whereas females performed most in the middle of the season. These results indicated that the sex of individuals initiating courtship changed seasonally, with courtship role reversal in the middle of the season. Intrasexual aggression in both sexes occurred much more frequently in mid-season than in the early and late seasons. Males frequently fought when available nest sites were limited, regardless of the presence of females, suggesting that males competed for nests in order to qualify to mate (resource competition). In contrast, courting females fought only in mid-season, when females' relative success in entering nests decreased, indicating that females competed for limited mating opportunities (mating competition). The reversed courtship roles and female mating competition in mid-season suggested that the sex roles in P. breviceps changed seasonally from the conventional roles to reversed roles and back again during one breeding season. This study provides the first empirical evidence of multiple changes in the sex roles of animals within a breeding season.     

The effects of farrowing nest size and width on sow and piglet behaviour and piglet survival

The ‘Werribee farrowing pen' (WFP) was developed as a loose housing alternative to the farrowing crate. The WFP occupies about twice the space of a crate and comprises two compartments, a ‘nest' and a ‘non-nest' area. In this experiment, we investigated the effects of reducing total pen space by modifying the dimensions of the ‘nest'. The hypothesis was that modifying ‘nest' size and width would not negatively affect piglet survival. A reduction in total floor space in the WFP may increase attractiveness for adoption of the system by pig producers. The experiment had a 2×2 factorial design with nine replicates and a total of 72 primiparous sows (Large White×Landrace) and their litters. All subjects were included to day 4 of lactation, but production data to weaning (day 23) was restricted to 36 litters. We examined the effects of ‘nest' size (large: L vs. small: S) and width (wide: W vs. narrow: N) on sow and piglet behaviours and piglet survival. The W, as compared to N treatment sows, had longer mean bouts of standing in the ‘nest' during 16–8 h pre-farrowing (3.7 vs. 2.0 min, P<0.01), suggesting that pre-farrowing (‘nesting') behaviour may have been adversely affected by narrow nest width. On the first 2 days of lactation, sow suckling grunts occurred more in the W than N treatment (14.1 and 8.0% of observations, P<0.01). However, this was due to an approximately 50% lower incidence in the SN treatment, as compared to the other treatments combined (5.9 and 12.7%). Piglets spent more (P<0.01) time at the udder in L vs. S (41 and 30%) and W vs. N nests (40 and 31%) and performed more (P<0.05) sucking behaviour (i.e., drinking milk from a teat) in L vs. S nests (2.5 and 1.2%). These differences were due to SN treatment litters sucking less than other treatments combined (0.9 vs. 2.2%). Of the 680 piglets born (n=72 litters), 3.8% were stillborn and 6.8% died between birth and day 4 of lactation. From day 5 to weaning (n=36 litters), 3.5% of piglets died, all due to Escherichia coli infection. While there were no effects of treatment on piglet survival, liveborn piglets were less likely (P<0.05) to die from E. coli in the L vs. S treatments (9/24 vs. 23/33 piglets). In conclusion, our results provide evidence that the size and width of the farrowing ‘nest' in a loose farrowing system may effect sow and piglet behaviours that may be relevant to piglet survival.     

The effects of spatial food distribution and group size on foraging behaviour in a benthic fish

Animals foraging in heterogeneous environments benefit from information on local resource density because it allows allocation of foraging effort to rich patches. In foraging groups, this information may be obtained by individuals through sampling or by observing the foraging behaviour of group members. We studied the foraging behaviour of goldfish (Carassius auratus) groups feeding in pools on resources distributed in patches. First, we determined if goldfish use sampling information to distinguish between patches of different qualities, and if this allowed goldfish to benefit from a heterogeneous resource distribution. Then, we tested if group size affected the time dedicated to food searching and ultimately foraging success. The decision of goldfish to leave a patch was affected by whether or not they found food, indicating that goldfish use an assessment rule. Giving-up density was higher when resources were highly heterogeneous, but overall gain was not affected by resource distribution. We did not observe any foraging benefits of larger groups, which indicate that grouping behaviour was driven by risk dilution. In larger groups the proportion searching for food was lower, which suggests interactions among group members. We conclude that competition between group members affects individual investments in food searching by introducing the possibility for alternative strategies, such as scrounging or resource monopolisation.     

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providingcare is costly, reducing parental growth and survival and, thereby,compromising future reproductive success. To determine if anexotic benthic predator might be affecting parental care bynest-guarding smallmouth bass (Micropterus dolomieu), we comparednest-guarding behavior and energy expenditures in two systems,one with a hyperabundant recently introduced predator, the roundgoby (Neogobious melanostomus). In Lake Erie, USA, smallmouthbass vigorously defended their nests from benthic round gobies.In Lake Opeongo, Canada, smallmouth bass were exposed to fewerand predominantly open-water predators and were less activein their nest defense. From scuba and video observations, wedocumented that nest-guarding smallmouth bass chased predators(99% of which were round gobies) nine times more frequentlyin Lake Erie than in Lake Opeongo. This heightened activityresulted in a significant decline in weight and energetic contentof guarding males in Lake Erie but no change in Lake Opeongomales. Bioenergetic simulations revealed that parental careincreased smallmouth bass standard metabolic rate by 210% inLake Erie but only by 28% in Lake Opeongo. As energy reservesdeclined and offspring became increasingly independent, malesin both lakes consumed more prey and spent more time foragingaway from their nests; however, nest-guarding smallmouth bassconsumed few prey and, in Lake Erie, rarely consumed round gobies.Therefore, increased parental care costs owing to the presenceof round gobies could affect future growth, reproduction, andsurvival if smallmouth bass approach critically low energy reserves.     

The effects of micro-gravity on hornet's nest building and activity

Principal scientific objectives: 1.) Comb building by hornet workers in micro-G: randomness of orientation, structural integrity, delay or rapidity of construction, all as a function of developmental state of the hornet. 2.) Dark-light effects on building hornets--will light provide building cues? 3.) Effect of domicile geometry on building practices--will the hornets build in spherical, domed or cube-shaped containers? 4.) Semiconductive properties of hornet cuticle and comb--will these be different than in the controls? Will the yellow granules developed in space be physico-chemically different from control granules? 5.) Post flight experiments--Will the hornets returned from space--build and oviposit as usual? Will the laid eggs embryonate? Will the comb be orientated as usual? How about other parameters of orientation (geotaxis) and social behavior (thigmotaxis)? Will there be any changes in the dominant gut microflora of returned hornets?     

Microsatellite markers and multiple paternity in a paternal care fish, Hexagrammos otakii

The fertilization success of sneaking behavior in a paternal care fish, Hexagrammos otakii, was estimated using microsatellites as genetic markers. Sneaking behavior was observed using a video camera placed near the nest of a breeding territorial male. Two egg masses fertilized by different patterns of sperm emission by the territorial male and sneaker males were examined for paternity discrimination. When a sneaker emitted a large amount of sperm after sperm emission by the territorial male, the sneaker fertilized more eggs than the territorial male. When the territorial male and a sneaker alternately emitted semen, the territorial male fertilized the most eggs. These results suggest that both the amount of emitted sperm and the timing of sperm emission are important factors in sperm competition. Received: November 18, 1999 / Accepted: January 17, 2000     

The effect of nest size on stone-gathering behaviour in the chinstrap penguin

Stone-collecting behaviour was studied in a colony of chinstrap penguins (Pygoscelis antarctica), to explore the likely importance of nest size. We randomly categorised nests as control or experimental. All nests were weighed at the beginning of the incubation period. In the experimental nests we removed stones constituting 50% of their initial weight, while in the control nests all the stones were returned after weighing. All nests were weighed again either prior to or just after hatching to determine likely changes in their weight. The mean weight increase of experimental nests was significantly higher than the mean weight increase of control nests. Size represents a property of the nest which individuals continuously monitor throughout the incubation/brooding period, reacting to changes in it by appropriate changes in stone-collecting rate. Accepted: 8 February 1999     

Effect of salinity on nest building behaviour in the nine-spined stickleback Pungitius sinensis

The authors evaluated the adaptability of male nine-spined sticklebacks (Pungitius sinensis) at three salinity levels (0, 5 and 10 psu) by comparing nest building success rates with nest structures. Successful nest building decreased as salinity increased. In addition, nests built in fresh water (i.e., 0 psu) were glued together, whereas those built in brackish water (5 and 10 psu) broke easily and fell from the nest site to the gravel bottom. Based on these findings, the authors suggest that P. sinensis adapts to freshwater environments.     

The effects of branches on prepartum nest building in gilts with access to straw

Sows farrowing in a semi-natural environment terminate nest building 1-7 h prior to parturition after having built a nest for which a variety of materials are used. No nest-building behaviour occurs during parturition and the sows remain lying in the nest throughout most of the farrowing. In contrast, many intensively housed sows are restless during farrowing. To investigate whether gilts housed indoors would use branches for nest building and whether access to branches would affect the termination of nest building and parturient behaviour, we studied gilts housed individually in pens designed to stimulate natural nest building. The control group (n=21) had unlimited access to straw and the experimental group (n=21) had unlimited access to straw and branches. During nest building all the gilts used straw and all the experimental gilts also used branches. In the experimental group the interval from termination of nest building to birth of the first piglet (BFP) was significantly longer than in the control group (132 versus 58 min, P=0.04). In the experimental group, nest-building behaviour was also performed by fewer individuals during the interval from BFP until 2 h after than in the control group (38% versus 71% of the gilts, P=0.03). Gilts that performed nest building during this interval carried out more postural changes (P<0.001) and spent less time in lateral recumbency (P=0.001) than gilts which did not perform nest building. On average, gilts that performed nest building behaviour after BFP (n=26) spent 54% of the first 2 h of parturition in lateral recumbency and carried out 16 postural changes. Gilts that did not perform nest building behaviour during this interval (n=16) spent 85% of the time in lateral recumbency and carried out five postural changes. In 10 gilts that were selected randomly from the experimental group nest building was studied in more detail. In these gilts nest building peaked between 17 and 6 h prepartum. There was no difference in amount of behaviour directed towards straw and amount of behaviour directed towards branches.The results indicate that the termination of nest building in sows is under environmental feedback control. When only straw was provided the nests did not have much of a lasting structure. However, when gilts had access to straw and branches more structured and functional nests could be built. These nests may have been more effective in reducing the motivation for nest building prior to the onset of parturition.