Why do Horsfield’s bronze-cuckoo <Emphasis Type="Italic">Chalcites basalis</Emphasis> eggs mimic those of their hosts?

The Horsfield’s bronze-cuckoo (Chalcites basalis) egg closely matches the appearance of its host fairy-wren (Malurus spp.) eggs. Mimicry of host eggs by cuckoos is usually attributed to coevolution between cuckoos and hosts, with host discrimination against odd-looking eggs selecting for ever better mimicry by cuckoos. However, this process cannot explain Horsfield’s bronze-cuckoo egg mimicry because fairy-wren hosts rarely reject odd-looking eggs from their nest. An alternative hypothesis is that cuckoos have evolved egg mimicry to disguise their eggs from other cuckoos. Female cuckoos remove one egg from the nest during parasitism and would potentially benefit by selectively removing any cuckoo egg that has already been laid in the nest because otherwise, their egg will be evicted by the first nestling cuckoo along with the host clutch. We used painted, non-mimetic eggs to test whether cuckoos selectively remove odd-looking eggs during parasitism. We found that they were no more likely to remove a non-mimetic egg from a superb fairy-wren Malurus cyaneus clutch than would be expected by chance. Thus, our study does not support the cuckoo egg replacement hypothesis to explain mimicry of host eggs by cuckoos.     

Incubation behavior,brood patch formation and obligate brood reduction in Fiordland crested penguins

Summary The first-laid eggs of Eudyptes penguins are much smaller than second eggs, generally hatch later, and experience greater mortality, features that characterize a brood reduction system unlike that of any other avian group. Hypotheses that (1) first-egg mortality is incidental to aggressive behavior by nesting birds and (2) hatching asynchrony is created by preferential egg treatment during incubation were tested in a colony of Fiordland crested penguins (E. pachyrhynchus). Neither hypothesis was supported. Although first eggs experienced greater mortality than second eggs, losses were not associated with aggressive behavior or the degree of nest crowding. First eggs hatched later than second eggs and were found more often in the anterior (previously assumed inferior) nest position. However, that position was not thermally disadvantaged, nor were lower temperatures consistently recorded from the smaller eggs. Parental brood patches did not form until after the first egg was laid; this delay may be a causal factor in the evolution of the unique reversal in eudyptid egg dimorphism.     

Seasonal variation in male-female competition,cooperation and selfish hoarding in a monogamous songbird

Both cooperation and conflict between the sexes are commonplace in monogamous mating systems. However, little is known about how cooperation and competition varies seasonally in monogamous species that maintain permanent territories. We presented territorial pairs of male and female New Zealand robins (Petroica australis) with a large supply of insect prey at monthly intervals for 2 years. Behavioural observations after food presentation were then made to quantify seasonal and sexual differences in aggressive interactions over prey, prey acquisition rates, mate provisioning, offspring provisioning, selfish food hoarding and cache retrieval. Data were used to evaluate sex-specific behavioural strategies of mediating competition for food. Results showed that males aggressively excluded females from experimental food sources year-round. Females only accessed food sources when males left them unattended. Consequently, females acquired fewer prey than males. After controlling for differences in prey acquisition, both sexes consumed similar amounts of prey in the non-breeding season. Even though males aggressively excluded females from accessing food sources directly, males fed large amounts of prey to females during the breeding season. Both sexes provisioned young at similar rates. Males cached less prey than females in the breeding season but more prey than females in the non-breeding season. Females showed similar caching intensities year-round. Although males tried to defend their hoards, females frequently retrieved male-made caches. Overall, results showed that although New Zealand robins cooperate to raise offspring during the breeding season, conflict between the sexes occurs year-round. Males and females display different behavioural strategies to gain access to experimental food sources, which appear to lessen male–female competition for food and evenly distribute food resources between the sexes.     

Sex-biased costs in nest defence behaviours by lesser snow geese (Chen caerulescens): consequences of parental roles?

Nest defence behaviours, such as attacking predators and defending against predator attacks, expose birds to risk of injury and death. However, direct costs of such behaviours are poorly documented. To evaluate potential costs of nest defence behaviours in lesser snow geese (Chen caerulescens), we (1) estimated the proportion of interactions between arctic foxes (Alopex lagopus) and geese that resulted in physical contact and (2) examined how nest defence behaviours varied between male and female geese. We separated interactions into attacks initiated by foxes (attacks by foxes) and attacks initiated by geese (attacks by geese). Risks associated with attacks by geese were considerably lower than the risks associated with attacks by foxes; only 1 of 1,179 attacks by geese resulted in physical contact between foxes and geese, whereas 26 of 89 attacks by foxes involved such contact (two female geese were killed during these attacks). Attacks by geese were made almost exclusively by male geese (>97%), whereas female geese were involved in 75% of all attacks by foxes that resulted in physical contact with geese. There was, thus, a considerable difference in risks associated with male and female nest defence behaviours. We suggest that parental roles during nesting (i.e., females incubate and males guard) expose female geese to greater risk of injury and death. Male geese may, however, reduce the risk of injury or death to their mates with pre-emptive attacks on foraging foxes.     

Management of fat reserves in tufted titmice (Parus bicolor ): evidence against a trade-off with food hoards

Caching species can manage their energy supply by adjusting body fat, number of caches, or both. It has been hypothesized that because body fat has a higher fitness cost than caches, small food-hoarding birds respond to increased starvation risk by increasing the number of their caches rather than their fat load. This hypothesis predicts that when birds cannot cache they should compensate for the loss of external energy storage by (1) shifting the time of their daily body mass accumulation toward earlier in the day and (2) increasing the overall level of their fat reserves. During the winter of 1995–1996, we tested these predictions with a caching species, the tufted titmouse (Parus bicolor). Each of six experimental birds was fed a diet of uncachable sunflower seed powder for 6 days, preceded and followed by 6-day control periods during which they were fed cachable sunflower seeds. The daily pattern of body mass gain was unaffected by the opportunity to cache. Furthermore, when unable to cache, the birds did not increase either their mean daily body mass, body mass in the middle of the day, or evening body mass compared to the two control periods. These results argue against the hypothesis of a trade-off between fat reserves and food caches in tufted titmice, and suggest that fat reserves are managed independently of external food caches. Received: 9 April 1997 / Accepted after revision: 30 August 1997     

Disentangling trophic relationships in a High Arctic tundra ecosystem through food web modeling

Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator-prey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.     

Egg adoption can explain joint egg-laying in common eiders

Hypotheses regarding the evolution and maintenance of intraspecific nest parasitism were tested with data collected during a 3-year study of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The nest parasitism rate was highest (42.4% of nests) during the year with the highest nest density and the best environmental conditions, and lowest (20.2% of nests) in the year with the lowest nest density and the poorest environmental conditions. Over the nesting season, parasitic eggs were laid at the same time as normally laid eggs. Most parasitic eggs (>75%) were laid before the host female laid her third egg. The majority of the parasitic eggs were the first or second egg produced by the parasitic female. When a parasitic egg was laid before or on the same day as the host female initiated her clutch, the probability of her first egg being depredated before incubation was significantly lowered. First- and second-laid eggs suffered a high rate of predation probably because nesting females do not attend their clutch until their second or third egg is laid. Hypotheses that some females use intraspecific nest parasitism to parasitize the parental care of other females were inconsistent with these data. Egg adoption is a likely explanation for the prevalence of females incubating parasitic eggs in this population. Received: 30 September 1997 / Accepted after revision: 6 May 1998     

Male spottail darters (Etheostoma squamiceps) do not use chemical or positional cues to discriminate between sired and foster eggs

Filial cannibalism is hypothesized to allow nest-guarding males to recoup energy lost during nest defense. Males in many species of fishes occasionally defend broods containing both sired and foster eggs due to shifts in nest site ownership or cuckoldry. Such males are predicted to consume primarily foster eggs if the ability to discriminate among eggs exists. In a previous laboratory study, male spottail darters (Etheostoma squamiceps) consumed significantly more foster eggs than sired eggs, suggesting the existence of a mechanism for discrimination using chemical or positional cues. This discrimination mechanism in the spottail darter was tested by creating nest sites with half sired eggs and half foster eggs (n=15), or with all sired eggs with half positionally relocated (n=9). Males defended these nests for 2 days in the field, and cannibalism was determined by counting eggs lost during that interval. Neither foster eggs nor relocated sired eggs were consumed in greater numbers or percentages of the original brood sizes than the unchanged sired eggs, indicating that male spottail darters do not discriminate between foster and sired eggs by olfaction or position. Alternatively, the hypothesis that males treat all eggs in nest sites in which they have spawned as sired explains the results of both studies.     

Tactics of parasitic American coots: host choice and the pattern of egg dispersion among host nests

Summary I examined the tactics adopted by a conspecific brood parasite, the American coot (Fulica americana), and the degree to which these tactics reflect sources of mortality for parasitic eggs. Only 8% of parasitic eggs produced independent offspring, compared to a 35% success rate for non-parasitic eggs, and most mortality was due to egg-rejection by hosts or the consequences of laying eggs too late in the host's nesting cycle. Parasites usually laid parasitically before initiating their own nests and usually parasitized immediate neighbours. Parasites did not remove host eggs before laying their own egg, and egg disappearance in general was not more common at parasitized nests. I found no evidence for non-random host choice, either on the basis of stage of the host's nesting cycle or the host's brood size. The absence of adaptive host choice is likely a consequence of the fact that, due to host limitation, only a small proportion of parasites had meaningful variation among potential hosts to choose from. The pattern of egg dispersion among host nests by individual parasites appears to be a compromise between constraints imposed by host limitation and the increased success obtained from spreading eggs among nests. Most females laying fewer than five parasitic eggs laid them in a single host nest while females laying five or more eggs normally parasitized two or more hosts. An examination of egg rejection and survival rates showed that parasites would maximize success by laying a single egg per host nest, and the pattern of laying several eggs per host nest is likely a consequence of host limitation. However, no egg that was the fifth laid, or later, parasitic egg in a host nest was ever successful and this probably explains why most females laying five or more eggs parasitized more than one host.     

Female cannibalism and male courtship tactics in threespine sticklebacks

Summary Female threespine sticklebacks (Gasterosteus aculeatus) frequently raid male nests and eat all the eggs therein. We tested the hypothesis of Vickery et al. (1988) that females prefer to raid nests containing large numbers of eggs than ones with smaller numbers of eggs. This hypothesis is based on the finding that females spawning in nests containing many eggs will have reduced hatching success because of egg crowding. By consuming the male's eggs and forcing him to rebuild his nest, raiding females might obtain a new opportunity to spawn under better conditions. Our results were consistent with the first prediction of this hypothesis that females were more likely to spawn in nests containing fewer eggs than in nests with many eggs. However, this may be the result of males becoming less receptive to females as the number of eggs in their nests increases. Prediction 2 was that females should raid those nests containing the most eggs. Contrary to this prediction, males defending only one clutch were as likely to have their nests raided by groups of females as males defending several clutches of eggs. Female cannibalism is therefore unlikely to have evolved as a means of gaining access to a male defending a small number of eggs. We also examined the tactics used by males to counter female raids. Most raids occur when the male is courting, and nests are more vulnerable to shoals of females than to single females. Therefore, we hypothesized that males with eggs preferentially court a single female rather than large groups of females, and that males without eggs court both groups indiscriminately. We also predicted that males restrict the number of females they mate with when risk of having their nest raided is high. Our results indicate that: (1) both males with eggs and those without eggs minimize the risk of female cannibalism by courting solitary females rather than groups of females and (2) males limit the number of females that lay eggs in their nest when several potentially raiding females are present. Offprint requests to: G.J. FitzGerald     

Interspecific competition in tree squirrels: do introduced grey squirrels (<Emphasis Type="Italic">Sciurus carolinensis</Emphasis>) deplete tree seeds hoarded by red squirrels (<Emphasis Type="Italic">S. vulgaris</Emphasis>)?

Red squirrels (Sciurus vulgaris) and introduced eastern grey squirrels (S. carolinensis) scatterhoard seeds of broadleaf trees. Scatterhoarded seeds are an essential resource in spring and their consumption increases red-squirrel fitness. We examined whether grey squirrels partly deplete the high-energy food resources cached by red squirrels, reducing their consumption, in two ways: (1) at the population level, comparing energy intake of feeding on cached seeds between a study site with red and grey squirrels and one with only red squirrels present; and (2) at the individual level, in the study site where species co-exist, relating hoard recovery of red squirrels to the amount of core-area overlap with grey squirrels. There were no significant site differences in the mean daily energy intake of red squirrels feeding on seeds recovered from caches. However, in the red-grey site, during spring, red squirrels that had a high percentage of their home-range core area overlapped by grey squirrels had a lower daily energy intake than low-overlap red squirrels. Body mass of red squirrels in spring was negatively correlated with the percentage of interspecific core-area overlap, but not with core-area overlap with other red squirrels. Our data suggest that interspecific competition for scatterhoarded seeds, with grey squirrels pilfering red squirrels' food caches, caused a reduced energy intake in red squirrels with a high degree of interspecific core-area overlap, and reduced body mass in spring. Therefore, cache pilfering is likely to reduce reproductive output in red squirrels, and thus play a role in the replacement of red by grey squirrels. Electronic Publication     

Adaptations of meadow pipits to parasitism by the common cuckoo

Summary The meadow pipit Anthus pratensis is one of the most frequent hosts in Europe parasitized by the common cuckoo Cuculus canorus. The cuckoo normally removes one or more of the host eggs and replaces them with one of its own. The aim of the present study, which was conducted in an upland area of Central Norway, was to test the following question: assuming the cuckoo has laid a mimetic egg (which is slightly larger than and slightly different in color from that of a meadow pipit egg), under what circumstances are the parent meadow pipits able to detect such parasitism? The reaction of the meadow pipits to artificial parasitism was tested. Plastic model cuckoo eggs were used that bore a striking resemblance to real cuckoo eggs found in other meadow pipit nests in the same area. In addition, in some experiments a stuffed cuckoo dummy was used. The meadow pipits tolerated the experimental procedures and remained in their nests when given an artificial cuckoo egg, with or without removal of one of the host's eggs. However, when a host egg was removed and replaced with an artificial cuckoo egg, and at the same time a stuffed cuckoo dummy was presente, 50% of the birds deserted their nests. The difference between this result and the results of the other experiments was statistically significant. When only the stuffed cuckoo was presented, without any egg manipulations, the meadow pipits reacted in the same way as in the egg experiments. We conclude that the meadow pipit is capable of detecting whether or not its nest has been parasitized, provided it has observed the cuckoo near the nest site. Furthermore, because of the results of our experiments, we reject the hypothesis that the cuckoo has evolved egg removal behavior in order to prevent the host from assessing an increase in egg numbers.     

Reduced nest defence intensity and improved breeding success in terns as responses to removal of non-native American mink

Lack of parental experience or differences in reproductive effort may lead to variation in nest defence behaviour among individuals in a prey population. In this experimental study, we analysed nest defence behaviour using a model of an American mink, Mustela vison, a non-native predator, at colonies of arctic terns, Sterna paradisaea, in two large areas where mink had been removed and two comparable control areas with mink in the south-western archipelago of Finland, Baltic Sea, in June 2000. Furthermore, we recorded breeding success of arctic terns in the same four areas during 1998–2001. Arctic terns took higher risks in nest defence in control areas and in a short-term (mink-free for 2 years) removal area than in the long-term (mink-free for 8 years) removal area. Thus, colonies with recent experience of mink were more active in defending their offspring. The breeding success of arctic terns was significantly higher in mink-removal areas than in control areas. We conclude that arctic terns modify their nest defence behaviour in the presence of mink. However, they cannot defend their nests sufficiently against this mainly nocturnal predator, since their breeding success is reduced in areas where mink are present.Communicated by J. Graves     

Egg coloration in ring-billed gulls (<Emphasis Type="Italic">Larus delawarensis</Emphasis>): a test of the sexual signaling hypothesis

Although many avian eggs appear to be cryptically colored, many species also lay vibrant blue green eggs. This seemingly conspicuous coloration has puzzled biologists since Wallace, as natural selection should favor reduced egg visibility to minimize predation pressure. The sexual signaling hypothesis posits that blue green egg coloration serves as a signal of female quality and that males exert post-mating sexual selection on this trait by investing more in the nests of females laying more intensely blue green eggs. This hypothesis has received mixed support to date, and most previous studies have been conducted in cavity-nesting species where male evaluation of his partner’s egg coloration, relative to that of other females, may be somewhat limited. In this study, we test the sexual signaling hypothesis in colonially nesting ring-billed gulls (Larus delawarensis) where males have ample opportunity to assess their mate’s egg coloration relative to that of other females. We used correlational data and an experimental manipulation to test four assumptions and predictions of the sexual signaling hypothesis: (1) blue green pigmentation should be limiting to females; (2) extent of blue green egg coloration should relate to female quality; (3) extent of blue green egg coloration should relate to offspring quality; and (4) males should provide more care to clutches with higher blue green chroma. Our data provide little support for these predictions of the sexual signaling hypothesis in ring-billed gulls. In light of this and other empirical data, we encourage future studies to consider additional hypotheses for the evolution of blue green egg coloration.     

Nest and maternal origin can influence morphology and locomotor performance of hatchling green turtles (Chelonia mydas) incubated in field nests

In numerous laboratory experiments involving the incubation of reptile eggs, both the maternal origin of eggs and the incubating environment (nest effect) have been demonstrated to influence hatchling phenotype. Although different hatchling phenotypes have been reported from natural nests, the separate effects of maternal origin and nest on hatchling phenotype in natural nests have not been demonstrated because in natural nests the two effects are confounded with each other. Here, we use a split clutch design to experimentally separate nest effects from maternal origin effects in field nests of green turtles (Chelonia mydas). We found both maternal origin and nest to influence hatchling morphology and locomotor performance in some but not all field nests. By using egg mass (maternal origin effect) and nest temperature (nest effect) in multiple regression analysis, we found maternal origin had a greater influence than nest temperature on the morphological attributes of hatchling mass and carapace size, but nest temperature had a greater influence than maternal origin on the performance attributes of self-righting time, self-righting propensity, swim thrust during the first 30 min of swimming, and power stroke rate during the first 30 min of swimming.     

Dynamics of biparental care in the dampwood termite,Zootermopsis nevadensis (Hagen): response to nitrogen availability

Summary Studies were conducted on the dampwood termite, Zootermopsis nevadensis, to examine the behavioral roles of the reproductive pair during the nest-founding period and to determine the effect of nitrogen availability on their reproduction and division of labor. Nitrogen has been hypothesized to be an important limiting nutrient for founding pairs. One nitrogenous reserve, uric acid-nitrogen, was examined in reproductives and in nutrient-receiving and nutrient-gathering colony members; it was found in highest amounts in the reproductives (i.e., alates, de-alates, and primary reproductives). Young pairs may use these nitrogenous reserves to increase their chances for reproduction. In support of this hypothesis, founding pairs that were fed a diet supplemented with uric acid-nitrogen had a significantly greater probability of producing at least one offspring than did pairs fed an unsupplemented diet. Females that were fed a nitrogen-poor diet restricted their total activity while their mates sustained a high activity during colony initiation. When fed a nitrogen-rich diet, females collected pulp more often than their mates, while males collected more water, though only in the period prior to egg laying. In all pairs, males transferred proctodeal pellets (food derived from the hindgut intestine) to their mates significantly more often than females to males, and females fed on proctodeal pellets significantly more often than did their mates. The male-female asymmetries in pellet transfer and feeding were not significant in the stage after egg deposition. Once eggs and larvae were present in the nest, a male and female spend an equal percentage of time caring for eggs and feeding larvae. Proctodeal pellets examined in reproductives were found to be rich in proteins. This suggests that in the pre-egg period, the male provides nitrogen-rich substances to the female as a form of paternal investment.     

Brood defense and filial cannibalism in the spottail darter (<Emphasis Type="Italic">Etheostoma squamiceps)</Emphasis>: the effects of parental status and prior experience

Male spottail darters (Etheostoma squamiceps) defend nest sites in which females deposit eggs over the course of several weeks. In laboratory experiments, I tested three predictions of the hypothesis that the presence of eggs increases the value of a nest site to male spottail darters: (1) males should preferentially defend nests with eggs over empty nests, and males that sired the eggs should (2) spend more time defending them and (3) consume less of their broods than should alloparent males. Parent males were tested using eggs they were guarding in the field; alloparents included males that were not defending eggs immediately prior to the experiment (inexperienced), and males that were defending eggs in the field when captured but were given eggs sired by a different male (experienced). In choice experiments in which males were offered nest sites differing only in the presence of eggs, males preferred to defend nest sites with eggs regardless of parental status. Parent males spent significantly more time defending eggs and consumed less of their broods than did inexperienced alloparent males. Experienced alloparent males were similar to parent males in brood defense but had levels of filial cannibalism similar to inexperienced males, suggesting that prior experience may influence brood defense but not egg consumption.     

Algal blooms decrease care but increase egg survival in a fish with paternal care

Human-induced eutrophication, resulting in algal blooms and increased water turbidity, is an alarming problem in aquatic systems. Here, we experimentally tested the impact of algal turbidity on parental care, egg fanning, and time in the nest, in the sand goby, Pomatoschistus minutus, a fish with uniparental male care. We allowed males to care for their eggs in either clear water or water made turbid by planktonic algae. In the early brood cycle, males fanned their eggs less in turbid than in clear water, but this difference disappeared later. Despite decreased care, egg survival was higher in turbid conditions, indicating that early fanning may partly be redundant for egg survival and perhaps used more as courtship. Males also spent more time out of their nest in turbid water, perhaps as a means to encounter additional females under conditions of low visibility.     

Blue eggs do not reduce nest predation in the song thrush,Turdus philomelos

Summary Many passerine birds with open cup-shaped nests lay blue or blue-green eggs. In thrushes, blue eggs may be cryptic and provide camouflage by imitating spots of light on green leaves. Alternatively, egg coloration may be selectively neutral because nest predators detect nests and not eggs, or it may be maladaptive because organisms are not always well adapted to their present environment. I evaluated these hypotheses by studying predation on artificial song thrush (Turdus philomelos) nests with quail eggs, painted either white, blue, or spotted (cryptic to a human eye). Corvids were the major nest predators. For concealed as well as exposed nests, I found no differences in the predation rates of nests with white, blue, or spotted eggs. Predators apparently detected the nests, and not the eggs, first. In a second experiment, I placed egg groups without nests in trees to study the effect of color per se. The predation rate of the spotted egg groups was significantly lower than that of the white and blue egg groups, for concealed as well as exposed egg groups. These results suggest that blue eggs in the song thrush are not cryptic but may be selectively neutral or even maladaptive with regard to nest predation.     

Active protection of unrelated offspring against parasitoids. A byproduct of self defense?

Natural enemies exert selection pressure on their prey. Predators and parasitoids drive their prey into the evolution of novel traits to cope with this stress. When eggs and juveniles are the target of enemies, defense strategies may rely on adults. However, it is not easy to predict whether adults should actively protect unrelated offspring. Females of the golden egg bug (Phyllomorpha laciniata) mainly oviposit on conspecifics of either sex. Females can also lay eggs on their food plant. Eggs placed on plants suffer from a higher mortality caused by natural enemies than eggs carried by bugs. Females never carry their own eggs and males are seldom related to the eggs they carry. We experimentally explored if conspecifics protect the eggs by studying the behavioral interaction between P. laciniata individuals and the specialist egg parasitoid Gryon bolivari. All bugs exhibited active responses against parasitoids regardless of the sex of the bug, the egg load, and their mating status. Most of the responses prevented parasitoids from reaching the eggs, and thus they reduced the risk of egg parasitization. Although responses of bugs were effective to overcome parasitoid attacks, we suggest that egg protection against parasitoids has evolved as a co-opted trait from a general defense of adult bugs against enemies. In this system, egg defense is not an individual's strategy to protect the offspring, but rather a consequence of the eggs being attached to one's body. It may also explain the low parasitization carried eggs suffer in the wild. The results further highlight the idea of conspecifics as an enemy-free space in P. laciniata.