Reproductive Benefits Research Articles

Competition decreases with relatedness and lek size in mole crickets: a role for kin selection?

Are “leks,” where males advertise in groups for females to gain mating opportunities, the result of competition, or cooperation? In the prairie mole cricket Gryllotalpa major, we present evidence that 1) males display near relatives and 2) males on smaller, more highly related leks experience lower levels of competition. These data suggest that kin selection may be operating within kin clusters on leks and males likely gain a reproductive benefit by displaying nearby relatives.

Which male and female characteristics influence the probability of extragroup paternities in rhesus macaques, Macaca mulatta?

Extragroup paternity (EGP) is found across a wide range of species and may entail reproductive benefits, but may also entail costs to both sexes. While population and group parameters affecting the degree of EGPs are relatively well established, less is known about the individual characteristics that make males and females engage in alternative reproductive tactics such as EGP. Applying a combination of long-term demographic and genetic data from the rhesus macaque population of Cayo Santiago (Puerto Rico, U.S.A.), we investigate which male and female characteristics influence the probability of EGP to better understand the circumstances that shape the distribution and occurrence of EGP. Our results show that, against our expectations, higher-ranking females were more likely to produce EGP offspring than lower- ranking females. The probability of producing extragroup offspring was not significantly related to female or male age, male tenure or previous reproductive success. Furthermore, genetic relatedness between the parents did not affect the production of extragroup offspring, but extragroup offspring were more frequently produced early rather than late in a given mating season. Altogether, our analysis suggests that individual attributes and seasonal aspects create different opportunities and preferences for engaging in EGP as an alternative reproductive tactic. The observed patterns of EGP in rhesus macaques appear to be consistent with female mate choice for genetic benefits, which needs to be confirmed in future studies.

Pair bond endurance promotes cooperative food defense and inhibits conflict in coral reef butterflyfish

Pair bonding is generally linked to monogamous mating systems, where the reproductive benefits of extended mate guarding and/or of bi-parental care are considered key adaptive functions. However, in some species, including coral reef butterflyfishes (f. Chaetodonitidae), pair bonding occurs in sexually immature and homosexual partners, and in the absence of parental care, suggesting there must be non-reproductive adaptive benefits of pair bonding. Here, we examined whether pair bonding butterflyfishes cooperate in defense of food, conferring direct benefits to one or both partners. We found that pairs of Chaetodon lunulatus and C. baronessa use contrasting cooperative strategies. In C. lunulatus, both partners mutually defend their territory, while in C. baronessa, males prioritize territory defence; conferring improvements in feeding and energy reserves in both sexes relative to solitary counterparts. We further demonstrate that partner fidelity contributes to this function by showing that re-pairing invokes intra-pair conflict and inhibits cooperatively-derived feeding benefits, and that partner endurance is required for these costs to abate. Overall, our results suggest that in butterflyfishes, pair bonding enhances cooperative defense of prey resources, ultimately benefiting both partners by improving food resource acquisition and energy reserves.

The economic value of replacement breeding ewes attaining puberty within their first year of life on New Zealand sheep farms

The economic value of increasing the reproductive performance of a breeding-ewe flock through selecting replacement ewes that attain puberty (AP) in their first year of life was quantified using bio-economic farm system modelling. In all of the scenarios modelled, the breeding-ewes were first presented for mating as yearlings (18–19 months of age) to enable them to start lambing at 2 years of age. For a New Zealand hill country sheep farm initially weaning 1.4 lambs per ewe mated, farm profit was improved by 6% when the percentage of breeding ewes that attained puberty in their first year of life was increased from 25% to 100%. However, if current sheep-industry target liveweight recommendations for rearing ewe lambs are met then between 70 and 95% of breeding-ewes should already attain puberty in their first year of life, and under these circumstances any further gains in farm profitability through specifically using this selection policy will be small (<2%). Countering the reproductive performance benefits of this selection policy was: (1) ewe liveweight increased with a higher AP%, which increased the individual feed requirements of the ewes; and (2) ewe mortality increased as multiple-bearing ewes became increasingly prevalent. The economic cost of using additional resources to further increase the farm's feed supply outweighed the benefits, resulting in the need to reduce farm breeding ewe numbers. The methodology and farm system model used for this study can be readily applied to other sheep farming systems. This can identify components of the reproductive process which should be targeted for further research to maximise on-farm benefits, and provide information on how a farm system will need to change for this to be successfully achieved.

A general structured model of a hermaphrodite population

Both empirical and theoretical studies, have dealt with the question how to best optimize reproductive fitness for hermaphrodites, using models such as game theory or complicated energetic costs and benefits of mating displays. However, hermaphrodites exhibit a broad spectrum of sexual behaviors like simultaneous, sequential or lifetime gonochorist that cannot be explained using a unique formalism.A possible explanation of this diversity relies on the way these species maximize their fitness: Does the individual hermaphrodite split its time between strategies maximizing its instantaneous reproductive fitness or its evolutionary fitness?Here, we compare these two points of view and extend a game theoretical formalism to a sex allocation model that underlies all sexual behaviors as a result of a dynamic game whose payoff depends on the costs and benefits of sexual reproduction. Using this formalism, we prove that a simultaneous hermaphrodites strategy is stable even for high values of sex changing costs. Moreover, we prove that the stability of a sequential hermaphrodite is linked to the average energy allocated to the pure female strategy.

Closed-system drug-transfer devices plus safe handling of hazardous drugs versus safe handling alone for reducing exposure to infusional hazardous drugs in healthcare staff.

Closed-system drug-transfer devices plus safe handling of hazardous drugs versus safe handling alone for reducing exposure to infusional hazardous drugs in healthcare staff.

Novel predation opportunities in anthropogenic landscapes

Novel ecosystems (‘emerging ecosystems’) result when species occur in combinations and relative abundances that have not occurred previously within a given biome, due to deliberate or inadvertent human agency. Humans have changed the environment through disturbance, physical structures or additional resources. Many vertebrate predators inhabit cities, towns and other places that humans have built or altered, and make use of these anthropogenic niches. These predators range in size from bats swarming around lamp posts, to leopards stalking domestic animals in the heart of cities. In this essay, we describe four scenarios where predators opportunistically make use of anthropogenic niches. First, humans are surrounded by animals, including synanthropic rodents and birds, livestock and pets, that can be novel prey for opportunistic predators. Second, feeding on prey concentrations created through anthropogenic niches increases their hunting efficiency, by reducing both search and commute times. Third, anthropogenic environments create novel situations such as thermals and artificial lighting that advantage some predators, increasing their capture success. Finally, many predators have developed novel hunting strategies to make the most of opportunities in anthropogenic environments that can lead to greater hunting success. We give examples of these four scenarios and have developed a conceptual model that captures the common mechanisms relevant to each, with predictions for how these can be explored further in future studies. Predators exploiting anthropogenic niches can experience greater ease of hunting, decreased search effort and/or increased capture success. Consequently, these animals experience many physiological and reproductive benefits over conspecifics that do not make similar use of anthropogenic niches, ultimately benefitting from living alongside humans.

Protective effect of Lespedeza cuneata ethanol extract on Bisphenol A-induced testicular dysfunction in vivo and in vitro

PurposeBisphenol A (BPA) has been regarded as a possible risk factor for reproductive health. We examined potential reproductive health benefits of Lespedeza cuneata ethanol extract (LCE). Previously, Lespedeza cuneata showed many therapeutic effects. However, the protective effect of LCE on BPA-induced testicular dysfunction and its mechanisms have not been precisely studied. MethodsMice were randomly divided into six groups (n = 7). Sperm counts and motility were measured by light microscope. Testosterone, total cholesterol, triglycerides, HDL, LDL-cholesterol, glucose, free fatty acids, hs-CRP, Angiotensinogen, Angiotensin II, GOT, GPT, TBARS, GSH, CAT, and SOD1 were measured in mouse serum. The potential protective effects of the LCE on mouse sertoli cells were evaluated. ResultsOral administration of LCE in BPA-exposed male mice restored testis weight, sperm count, motility, and testosterone levels by inhibiting markers in serum. In addition, treatment with LCE in BPA-treated TM4 sertoli cells recovered cell viability by attenuating Bax expression and activating caspase 3 and PARP. ConclusionsThese results indicate that LCE prevented BPA-induced testicular dysfunction and cell viability in BPA-treated TM4 sertoli cells. Our study also suggests that LCE has the potential to protect male reproductive health.

Expected value of crossbred dairy cattle artificial insemination breeding strategies in virgin heifers and lactating cows

Research on sexed semen breeding techniques has largely focused on purebred cattle production systems and little work has been done evaluating sexed semen use in crossbred dairy cattle. Complementing a crossbreeding reproduction strategy with sexed semen artificial insemination (AI) has the potential to increase profit potential of sexed semen technology in the short and long run. The objective of this project was to estimate and compare the expected net present value (NPV) of reproduction management programs considering several conventional and sexed semen breeding strategies, cow ages, and breed compositions. While the potential benefits of sexed semen are varied, it is important to note that the focus of this study is on the economic returns to the breeding program. This is not a life-cycle analysis, and therefore, only the sexed semen costs and returns that directly impact the returns to the breeding program are considered. Specifically, a NPV model that incorporates dystocia and stillbirth costs, in addition to improved fertility of crossbred cattle (over purebred cattle), directly into the expected NPV calculation is developed. Increased use of crossbred dairy cattle in the United States make this research particularly timely and relevant. Consistent with previous research, results indicate that pure conventional semen AI and a mixed strategy with one sexed semen AI followed by conventional semen were generally the preferred breeding strategies in terms of expected NPV across all breeds and dam ages evaluated. Similarly, our results also support previous findings that the expected NPV of breeding programs for virgin heifers were consistently higher than lactating cows. In terms of breeds, the crossbreed scenarios generally produced higher expected NPV than scenarios for purebred Holsteins. The most influential factors resulting in these higher returns were the higher cumulative pregnancy rates associated with the crossbreds. Reproductive benefits of crossbred dairy cattle may be able to alleviate some economic pressure currently associated with poor dairy reproduction with AI breeding strategies (especially those incorporating sexed semen). However, it is important to note the likely tradeoffs associated with improvements in fertility (e.g., reduced milk production), the consideration of which is necessary to maximize whole farm profitability.

Testing Cessation Messages for Cigarette Package Inserts: Findings from a Best/Worst Discrete Choice Experiment.

This study assessed smokers’ responses to different smoking cessation topics and imagery for cigarette package inserts. Adult smokers from Canada (n = 1000) participated in three discrete choice experiments (DCEs): DCE 1 assessed five cessation benefit topics and five imagery types; DCE 2 assessed five messages with tips to improve cessation success and five imagery types; DCE 3 assessed four reproductive health benefits of cessation topics and four imagery types. In each DCE, participants evaluated four or five sets of four inserts, selecting the most and least motivating (DCEs 1 & 3) or helpful (DCE 2) for quitting. Linear mixed models regressed choices on insert and smoker characteristics. For DCE 1, the most motivating messages involved novel disease topics and imagery of younger women. For DCE 2, topics of social support, stress reduction and nicotine replacement therapy were selected as most helpful, with no differences by imagery type. For DCE 3, imagery influenced choices more than topic, with imagery of a family or a mom and baby selected as most motivating. Statistically significant interactions for all three experiments indicated that the influence of imagery type on choices depended on the message topic. Messages to promote smoking cessation through cigarette pack inserts should consider specific combinations of message topic and imagery.

The consequences of sexual selection in well-adapted and maladapted populations of bean beetles†.

Whether sexual selection generally promotes or impedes population persistence remains an open question. Intralocus sexual conflict (IaSC) can render sexual selection in males detrimental to the population by increasing the frequency of alleles with positive effects on male reproductive success but negative effects on female fecundity. Recent modeling based on fitness landscape theory, however, indicates that the relative impact of IaSC may be reduced in maladapted populations and that sexual selection therefore might promote adaptation when it is most needed. Here, we test this prediction using bean beetles that had undergone 80 generations of experimental evolution on two alternative host plants. We isolated and assessed the effect of maladaptation on sex-specific strengths of selection and IaSC by cross-rearing the two experimental evolution regimes on the alternative hosts and estimating within-population genetic (co)variance for fitness in males and females. Two key predictions were upheld: males generally experienced stronger selection compared to females and maladaptation increased selection in females. However, maladaptation consistently decreased male-bias in the strength of selection and IaSC was not reduced in maladapted populations. These findings imply that sexual selection can be disrupted in stressful environmental conditions, thus reducing one of the potential benefits of sexual reproduction in maladapted populations.

Does stigma curvature promote delayed selfing? An experimental investigation in Triodanis perfoliata (Campanulaceae).

Self-fertilisation that is delayed until after opportunities for outcrossing have ceased has been argued to provide both the reproductive assurance benefits of selfing and the genetic advantages of outcrossing. In the Campanulaceae, presentation of pollen on stylar hairs and progressive stigma curvature have been hypothesised to facilitate delayed selfing, but experimental tests are lacking. Stigma curvature is common in Campanula, a genus largely characterised by self-incompatibility, and therefore is unlikely to have initially evolved to promote self-fertilisation. In derived self-compatible species, however, stigma curvature might serve the secondary function of delayed selfing. We investigated delayed selfing in Triodanis perfoliata, a self-compatible relative of Campanula. Using floral manipulation experiments and pollen tube observations, we quantified the extent and timing of self-pollination. Further, we hypothesised that, if stigma curvature provides the benefit of delayed selfing in Triodanis, selection should have favoured retention of self-pollen through the loss of a stylar hair retraction mechanism. Results of a stigma removal experiment indicated that autonomous selfing produces partial seed set, but only some selfing was delayed. Pollen tube observations and a flower senescence assay also supported the finding of partial delayed selfing. Scanning electron microscopy revealed that pollen-collecting hairs retract during anthesis, which may limit the extent of delayed selfing. Delayed selfing appeared to be only partially effective in T.perfoliata. The stylar hair retraction in this species would seem to contradict selection for selfing. We suggest that caution and rigour are needed in interpreting floral traits as adaptive mechanisms for delayed selfing.

Symbiont-conferred reproduction and fitness benefits can favour their host occurrence.

Double infections of Wolbachia and Spiroplasma are frequent in natural populations of Tetranychus truncatus, a polyphagous mite species that has been a dominant species in China since 2009. However, little is known about the causes and ecological importance of such coexistences. In this study, we established T. truncatus strains with different infection types and then inferred the impact of the two endosymbionts on host reproduction and fitness. Double infection induced cytoplasmic incompatibility, which was demonstrated by reduction in egg hatchability of incompatible crosses. However, doubly infected females produced more eggs relative to other strains. Wolbachia and Spiroplasma did not affect host survival, whereas doubly infected females and males developed faster than other strains. Such reproduction and fitness benefits provided by double infections may be associated with the lower densities of each symbiont, and the quantitative results also confirmed competition between Wolbachia and Spiroplasma in doubly infected females. These symbiont‐conferred beneficial effects maintain stable prevalence of the symbionts and also help drive T. truncatus outbreaks in combination with other environmental factors.

The influence of azaperone treatment at weaning on reproductive performance of sows: altering effects of season and parity

Azaperone treatment can control aggression and decrease stress due to weaning, re-grouping and hierarchical fighting of gilts and sows. However, the effects of this butyrophenone neuroleptic and sedative administered at weaning on pig reproductive function are poorly characterized. In this year-long study, a total of 619 cross-bred sows (Polish Large White×Polish Landrace) kept on a commercial farm received an i.m. injection of azaperone (Stresnil®; 2 mg/kg BW) just before weaning and were artificially inseminated during the ensuing estrus with 3×109 spermatozoa per dose of an inseminate; 1180 sows served as untreated controls. Immediately after weaning, the sows were moved to four pens of seven to nine animals each. A teaser boar was used twice daily to check for estrus and sows were bred at heat detection. Subsequently, all sows stayed in individual stalls until pregnancy testing on day 30 post-artificial insemination and were then re-grouped until farrowing. The proportion of pigs that were in estrus within 6 days post-weaning was significantly lower in azaperone-treated groups of animals than in controls (71.4% v. 84.2%). Overall, the azaperone-treated sows had a significantly longer weaning-to-estrus interval (WEI; 8.7±10.1 v. 6.3±8.1 days; mean±SD) and a significantly larger litter size (LS: 11.8±3.0 v.11.3±3.2; azaperone-treated v. control sows). Treatment of the winter-farrowing sows was associated with increased LS (12.8±2.6 and 11.3±3.1 piglets/sow, respectively; P<0.05) and longer (P<0.05) weaning-to-effective-service intervals (11.7±19.3 and 8.4±12.3 days, respectively) as well as farrowing intervals (155.7±19.7 and 152.2±16.1 days, respectively) compared with untreated controls. In the summer months, significantly longer WEIs (12.1±21.0 v. 8.4±16.9 days) were accompanied by a significant decline in LS only in azaperone-treated sows that were inseminated within 6 days post-weaning (10.8±2.9 v. 11.5±3.3 piglets/sow; azaperone-treated v. controls). Azaperone-treated second parity sows had greater LS (P<0.001) along with prolonged WEIs (P<0.05) in comparison to their respective controls, regardless of the timing of estrus. An application of azaperone at weaning increased the annual piglet productivity of winter-farrowing animals and of second parity sows but depressed it significantly in summer. The extra cost and labor due to delayed onset of estrus may cancel out any reproductive benefits of azaperone treatment.

When to Cheat: Modeling Dynamics of Paternity and Promiscuity in Socially Monogamous Prairie Voles (Microtus ochrogaster).

In many socially monogamous species, individuals form long-term pair bonds and males mate guard females. Such behavior is thought to help secure intra-pair fertilizations, the result of intra-pair copulations (IPCs), and ensure paternity. However, socially monogamous males are also often opportunistic and seek additional mating opportunities with other females, leaving their partner unguarded. The success associated with a male’s decision to seek more mates over guarding his partner might be impacted by the activity of other males, specifically the proportion of other males leaving their territories to seek extra-pair copulations (EPCs). The amount of EPC-seeking males can impact the likelihood of a given male encountering an unguarded paired female, but also of being cuckolded (losing IPCs). It remains unclear under which conditions it is optimal to stay and guard or seek EPCs. Using field data from socially monogamous prairie voles (Microtus ochrogaster) to generate parameters, we used optimal performance modeling (Monte Carlo simulations) to ask when is it most reproductively advantageous for a bonded male to seek EPCs, despite the risk of losing IPCs. We defined three types of males: exclusive mating bonded males (true residents), non-exclusive mating bonded residents (roving residents), and unpaired males (wanderers). We first modeled the success of an individual male living in a context that incorporated only true and roving residents. We next added wandering males to this model. Finally, we considered the effects of including wandering males and unpaired females in our model. For all contexts, we found that as EPC-seeking in the population increases, the potential reproductive benefit for seeking EPCs increasingly outpaces the rate of cuckolding. In other words, we observe a shift in optimal strategy from true residents to rovers among paired males. Our models also demonstrate that reproductive fitness is likely to remain constant, despite the shift toward obtaining success via EPCs over IPCs. Our results show the dynamic nature of reproductive decision-making, and demonstrate that alternative reproductive decisions yield subtle but important differences despite appearing as balanced strategies.

Distinct effects of the nephridial symbionts Verminephrobacter and Candidatus Nephrothrix on reproduction and maturation of its earthworm host Eisenia andrei.

Verminephrobacter, the most common specific symbionts in the nephridia (excretory organs) of lumbricid earthworms, have been shown to improve reproduction of the garden earthworm Aporrectodea tuberculata under nutrient limitation. It is unknown how general this beneficial trait is in the Verminephrobacter-earthworm symbiosis, whether other nephridial symbionts also affect host fitness and what the mechanism of the fitness increase is. Here we report beneficial effects of Verminephrobacter and Candidatus Nephrothrix on life history traits of the compost worm Eisenia andrei, which in addition to these two symbionts also hosts Agromyces-like bacteria in its mixed nephridial community: while growth was identical between control, Verminephrobacter-free and aposymbiotic worms, control worms produced significantly more cocoons and offspring than both Verminephrobacter-free and aposymbiotic worms, confirming the reproductive benefit of Verminephrobacter in a second host with different ecology and feeding behavior. Furthermore, worms with Verminephrobacter and Ca. Nephrothrix, or with only Ca. Nephrothrix present, reached sexual maturity significantly earlier than aposymbiotic worms; this is the first evidence for a beneficial role of Ca. Nephrothrix in earthworms. Riboflavin content in cocoons and whole earthworms was unaffected by the presence or absence of nephridial symbionts, suggesting that nutritional supplementation with this vitamin does not play a major role in this symbiosis.

The relationship between egg size and helper number in cooperative breeders: a meta-analysis across species.

BackgroundLife history theory predicts that mothers should adjust reproductive investment depending on benefits of current reproduction and costs of reduced future reproductive success. These costs and benefits may in turn depend on the breeding female’s social environment. Cooperative breeders provide an ideal system to test whether changes in maternal investment are associated with the social conditions mothers experience. As alloparental helpers assist in offspring care, larger groups might reduce reproductive costs for mothers or alternatively indicate attractive conditions for reproduction. Thus, mothers may show reduced (load-lightening) or increased (differential allocation) reproductive investment in relation to group size. A growing number of studies have investigated how cooperatively breeding mothers adjust pre-natal investment depending on group size. Our aim was to survey these studies to assess, first, whether mothers consistently reduce or increase pre-natal investment when in larger groups and, second, whether these changes relate to variation in post-natal investment.MethodsWe extracted data on the relationship between helper number and maternal pre-natal investment (egg size) from 12 studies on 10 species of cooperatively breeding vertebrates. We performed meta-analyses to calculate the overall estimated relationship between egg size and helper number, and to quantify variation among species. We also tested whether these relationships are stronger in species in which the addition of helpers is associated with significant changes in maternal and helper post-natal investment.ResultsAcross studies, there is a significant negative relationship between helper number and egg size, suggesting that in most instances mothers show reduced reproductive investment in larger groups, in particular in species in which mothers also show a significant reduction in post-natal investment. However, even in this limited sample, substantial variation exists in the relationship between helper number and egg size, and the overall effect appears to be driven by a few well-studied species.DiscussionOur results, albeit based on a small sample of studies and species, indicate that cooperatively breeding females tend to produce smaller eggs in larger groups. These findings on prenatal investment accord with previous studies showing similar load-lightening reductions in postnatal parental effort (leading to concealed helper effects), but do not provide empirical support for differential allocation. However, the considerable variation in effect size across studies suggests that maternal investment is mitigated by additional factors. Our findings indicate that variation in the social environment may influence life-history strategies and suggest that future studies investigating within-individual changes in maternal investment in cooperative breeders offer a fruitful avenue to study the role of adaptive plasticity.

Birds choose long-term partners years before breeding

Pair bonds can provide social benefits to long-term monogamous species alongside their benefits for reproduction. However, little is known about when these bonds form, in particular how long they are present before breeding. Previous studies of pair formation in long-term monogamous birds have been rather data-limited, but for many migratory birds they report pair formation on the wintering grounds. We provide the first systematic investigation of prebreeding association patterns of long-term monogamous pairs by examining entire life histories based on tracking data of migratory whooping cranes, Grus americana. We found that a substantial portion (62%) of breeding pairs started associating at least 12 months before first breeding, with 16 of 58 breeding pairs beginning to associate over 2 years before first breeding. For most pairs, these associations with future breeding partners also became unique and distinguishable from association patterns with nonpartner individuals 12 months before first breeding. In addition, 60% of pair associations began before at least one partner had reached nominal sexual maturity. Most pairs began associating in the late spring upon arrival at the summer grounds, while associations beginning at other times of the year were rare. Patterns in the associations of pairs prior to breeding can point to the potential benefits of prebreeding relationships, for instance providing support in competitive interactions or increasing partner familiarity.

Postnatal nutrition influences male attractiveness and promotes plasticity in male mating preferences.

Poor early-life nutrition could reduce adult reproductive success by negatively affecting traits linked to sexual attractiveness such as song complexity. If so, this might favor strategic mate choice, allowing males with less complex songs to tailor their mating tactics to maximize the reproductive benefits. However, this possibility has been ignored in theoretical and empirical studies. By manipulating the micronutrient content of the diet (e.g., low or high) during the postnatal period of male zebra finches, we show for the first time (1) that males reared on a poor (low) micronutrient diet had less complex songs as adults; (2) that these males, in contrast to the high micronutrient diet group, were more selective in their mating strategies, discriminating against those females most likely to reduce their clutch size when paired with males having less complex songs; and (3) that by following different mating strategies, males reared on the contrasting diets obtained similar reproductive benefits. These results suggest that early-life dietary conditions can induce multiple and long-lasting effects on male and female reproductive traits. Moreover, the results seem to reflect a previously unreported case of adaptive plasticity in mate choice in response to a nutritionally mediated reduction in sexual attractiveness.

Delayed dispersal and prolonged brood care in a family-living beetle.

Delayed juvenile dispersal is an important prerequisite for the evolution of family-based social systems, such as cooperative breeding and eusociality. In general, young adults forego dispersal if there are substantial benefits to remaining in the natal nest and/or the likelihood of dispersing and breeding successfully is low. We investigate some general factors thought to drive delayed juvenile dispersal in the horned passalus beetle, a family-living beetle in which young adults remain with their families in their natal nest for several months before dispersing. Fine-scale population genetic structure indicated high gene flow between nest sites, suggesting that constraints on mobility are unlikely to explain philopatry. Young adults do not breed in their natal log and likely disperse before reaching breeding age, suggesting that they do not gain direct reproductive benefits from delayed dispersal. We also examined several ways in which parents might incentivize delayed dispersal by providing prolonged care to adult offspring. Although adult beetles inhibit fungal growth in the colony by manipulating both the nest site and deceased conspecifics, this is unlikely to be a major explanation for family living as both parents and adult offspring seem capable of controlling fungal growth. Adult offspring that stayed with their family groups also neither gained more mass nor experienced faster exoskeleton development than those experimentally removed from their families. The results of these experiments suggest that our current understanding of the factors underlying prolonged family living may be insufficient to explain delayed dispersal in at least some taxa, particularly insects.