Guides and cheats: producer-scrounger dynamics in the human-honeyguide mutualism

Foraging animals commonly choose whether to find new food (as 'producers') or scavenge from others (as 'scroungers'), and this decision has ecological and evolutionary consequences. Understanding these tactic decisions is particularly vital for naturally occurring producer-scrounger systems of economic importance, because they determine the system's productivity and resilience. Here, we investigate how individuals' traits predict tactic decisions, and the consistency and pay-offs of these decisions, in the remarkable mutualism between humans (Homo sapiens) and greater honeyguides (Indicator indicator). Honeyguides can either guide people to bees' nests and eat the resulting beeswax (producing), or scavenge beeswax (scrounging). Our results suggest that honeyguides flexibly switched tactics, and that guiding yielded greater access to the beeswax. Birds with longer tarsi scrounged more, perhaps because they are more competitive. The lightest females rarely guided, possibly to avoid aggression, or because genetic matrilines may affect female body mass and behaviour in this species. Overall, aspects of this producer-scrounger system probably increase the productivity and resilience of the associated human-honeyguide mutualism, because the pay-offs incentivize producing, and tactic-switching increases the pool of potential producers. Broadly, our findings suggest that even where tactic-switching is prevalent and producing yields greater pay-offs, certain phenotypes may be predisposed to one tactic.

Social dominance and rainfall predict telomere dynamics in a cooperative arid-zone bird

In many vertebrate societies dominant individuals breed at substantially higher rates than subordinates, but whether this hastens ageing remains poorly understood. While frequent reproduction may trade off against somatic maintenance, the extraordinary fecundity and longevity of some social insect queens highlight that breeders need not always suffer more rapid somatic deterioration than their nonbreeding subordinates. Here, we used extensive longitudinal assessments of telomere dynamics to investigate the impact of dominance status on within-individual age-related changes in somatic integrity in a wild social bird, the white-browed sparrow-weaver (Plocepasser mahali). Dominant birds, who monopolise reproduction, had neither shorter telomeres nor faster telomere attrition rates over the long-term (1-5 years) than their subordinates. However, over shorter (half-year) time intervals dominants with shorter telomeres showed lower rates of telomere attrition (and evidence suggestive of telomere lengthening), while the same was not true among subordinates. Dominants may therefore invest more heavily in telomere length regulation (and/or somatic maintenance more broadly); a strategy that could mitigate the long-term costs of reproductive effort, leaving their long-term telomere dynamics comparable to those of subordinates. Consistent with the expectation that reproduction entails short-term costs to somatic integrity, telomere attrition rates were most severe for all birds during the breeding seasons of wetter years (rainfall is the key driver of reproductive activity in this arid-zone species). Our findings suggest that, even in vertebrate societies in which dominants monopolise reproduction, dominants may experience long-term somatic integrity trajectories indistinguishable from those of their nonreproductive subordinates.

When wax wanes: competitors for beeswax stabilize rather than jeopardize the honeyguide–human mutualism

Many mutualisms are exploited by third-party species, which benefit without providing anything in return. Exploitation can either destabilize or promote mutualisms, via mechanisms that are highly dependent on the ecological context. Here we study a remarkable bird–human mutualism, in which wax-eating greater honeyguides ( Indicator indicator ) guide humans ( Homo sapiens ) to wild bees' nests, in an exchange of knowledge about the location of nests for access to the wax combs inside. We test whether the depletion of wax by mammalian and avian exploiter species either threatens or stabilizes the mutualism. Using camera traps, we monitored feeding visits to wax comb made available following honey harvests. We found that greater honeyguides face competition for wax from conspecifics and nine exploiter species, five of which were not previously known to consume wax. Our results support the hypothesis that heterospecific exploiters stabilize the mutualism, because wax depletion by these competitors probably limits feeding opportunities for conspecific exploiters, favouring the early-arriving individual that guided humans to the bees’ nest. These findings highlight the importance of the ecological context of species interactions and provide further evidence for how mutualisms can persist because of, and not in spite of, exploitation by third-party species.

Safeguarding human–wildlife cooperation

Human–wildlife cooperation occurs when humans and free‐living wild animals actively coordinate their behavior to achieve a mutually beneficial outcome. These interactions provide important benefits to both the human and wildlife communities involved, have wider impacts on the local ecosystem, and represent a unique intersection of human and animal cultures. The remaining active forms are human–honeyguide and human–dolphin cooperation, but these are at risk of joining several inactive forms (including human–wolf and human–orca cooperation). Human–wildlife cooperation faces a unique set of conservation challenges, as it requires multiple components—a motivated human and wildlife partner, a suitable environment, and compatible interspecies knowledge—which face threats from ecological and cultural changes. To safeguard human–wildlife cooperation, we recommend: (i) establishing ethically sound conservation strategies together with the participating human communities; (ii) conserving opportunities for human and wildlife participation; (iii) protecting suitable environments; (iv) facilitating cultural transmission of traditional knowledge; (v) accessibly archiving Indigenous and scientific knowledge; and (vi) conducting long‐term empirical studies to better understand these interactions and identify threats. Tailored safeguarding plans are therefore necessary to protect these diverse and irreplaceable interactions. Broadly, our review highlights that efforts to conserve biological and cultural diversity should carefully consider interactions between human and animal cultures.

Please see AfricanHoneyguides.com/abstract‐translations for Kiswahili and Portuguese translations of the abstract.

Reproductive conflict resolution in cooperative breeders

Female infanticide is common in animal societies where groups comprise multiple co-breeding females. To reduce the risk that their offspring are killed, mothers can synchronize breeding and pool offspring, making it hard for females to avoid killing their own young. However, female reproductive conflict does not invariably result in reproductive synchrony, and we lack a general hypothesis explaining the variation in conflict resolution strategies seen across species. Here, we investigate the fitness consequences of birth timing relative to other females and the prevalence of birth synchrony in cooperatively breeding Kalahari meerkats (Suricata suricatta). We show that, although there would be substantial benefits to females in synchronizing births and reducing their risk of infanticide, birth synchrony is rare. Since precise breeding synchrony has evolved in a related species with similar infanticidal female reproductive conflict, its absence in meerkats requires an evolutionary explanation. We therefore explore the costs and benefits of synchronizing breeding in two theoretical models, each of which contrasts synchrony with an alternative reproductive strategy: (i) breeding opportunistically and accepting fitness losses to infanticide or (ii) suppressing the reproduction of others to prevent infanticide. Our models show that the costs of synchrony constrain its development if subordinates breed infrequently, and that selection instead favors the suppression of subordinate reproduction by the dominant and opportunistic reproduction by subordinates. Together, our results suggest that the resolution of reproductive conflict in animal societies is shaped by differential breeding propensities among female group members, leading to divergent conflict resolution strategies even in closely related species.

The development of individual differences in cooperative behaviour: maternal glucocorticoid hormones alter helping behaviour of offspring in wild meerkats

The phenotype of parents can have long-lasting effects on the development of offspring as well as on their behaviour, physiology and morphology as adults. In some cases, these changes may increase offspring fitness but, in others, they can elevate parental fitness at a cost to the fitness of their offspring. We show that in Kalahari meerkats ( Suricata suricatta), the circulating glucocorticoid (GC) hormones of pregnant females affect the growth and cooperative behaviour of their offspring. We performed a 3-year experiment in wild meerkats to test the hypothesis that GC-mediated maternal effects reduce the potential for offspring to reproduce directly and therefore cause them to exhibit more cooperative behaviour. Daughters (but not sons) born to mothers treated with cortisol during pregnancy grew more slowly early in life and exhibited significantly more of two types of cooperative behaviour (pup rearing and feeding) once they were adults compared to offspring from control mothers. They also had lower measures of GCs as they aged, which could explain the observed increases in cooperative behaviour. Because early life growth is a crucial determinant of fitness in female meerkats, our results indicate that GC-mediated maternal effects may reduce the fitness of offspring, but may elevate parental fitness as a consequence of increasing the cooperative behaviour of their daughters. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.

Effects of early-life competition and maternal nutrition on telomere lengths in wild meerkats

Early-life adversity can affect health, survival and fitness later in life, and recent evidence suggests that telomere attrition may link early conditions with their delayed consequences. Here, we investigate the link between early-life competition and telomere length in wild meerkats. Our results show that, when multiple females breed concurrently, increases in the number of pups in the group are associated with shorter telomeres in pups. Given that pups from different litters compete for access to milk, we tested whether this effect is due to nutritional constraints on maternal milk production, by experimentally supplementing females' diets during gestation and lactation. While control pups facing high competition had shorter telomeres, the negative effects of pup number on telomere lengths were absent when maternal nutrition was experimentally improved. Shortened pup telomeres were associated with reduced survival to adulthood, suggesting that early-life competition for nutrition has detrimental fitness consequences that are reflected in telomere lengths. Dominant females commonly kill pups born to subordinates, thereby reducing competition and increasing growth rates of their own pups. Our work suggests that an additional benefit of infanticide may be that it also reduces telomere shortening caused by competition for resources, with associated benefits for offspring ageing profiles and longevity.

The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder

Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies.

Oxidative stress and life histories: unresolved issues and current needs

Life‐history theory concerns the trade‐offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life‐history trade‐offs, but the details remain obscure. As life‐history theory concerns aspects of investment in the soma that influence survival, understanding the physiological basis of life histories is related, but not identical, to understanding the process of aging. One idea from the field of aging that has gained considerable traction in the area of life histories is that life‐history trade‐offs may be mediated by free radical production and oxidative stress. We outline here developments in this field and summarize a number of important unresolved issues that may guide future research efforts. The issues are as follows. First, different tissues and macromolecular targets of oxidative stress respond differently during reproduction. The functional significance of these changes, however, remains uncertain. Consequently there is a need for studies that link oxidative stress measurements to functional outcomes, such as survival. Second, measurements of oxidative stress are often highly invasive or terminal. Terminal studies of oxidative stress in wild animals, where detailed life‐history information is available, cannot generally be performed without compromising the aims of the studies that generated the life‐history data. There is a need therefore for novel non‐invasive measurements of multi‐tissue oxidative stress. Third, laboratory studies provide unrivaled opportunities for experimental manipulation but may fail to expose the physiology underpinning life‐history effects, because of the benign laboratory environment. Fourth, the idea that oxidative stress might underlie life‐history trade‐offs does not make specific enough predictions that are amenable to testing. Moreover, there is a paucity of good alternative theoretical models on which contrasting predictions might be based. Fifth, there is an enormous diversity of life‐history variation to test the idea that oxidative stress may be a key mediator. So far we have only scratched the surface. Broadening the scope may reveal new strategies linked to the processes of oxidative damage and repair. Finally, understanding the trade‐offs in life histories and understanding the process of aging are related but not identical questions. Scientists inhabiting these two spheres of activity seldom collide, yet they have much to learn from each other.

Immune response in a wild bird is predicted by oxidative status, but does not cause oxidative stress

The immune system provides vital protection against pathogens, but extensive evidence suggests that mounting immune responses can entail survival and fecundity costs. The physiological mechanisms that underpin these costs remain poorly understood, despite their potentially important role in shaping life-histories. Recent studies involving laboratory models highlight the possibility that oxidative stress could mediate these costs, as immune-activation can increase the production of reactive oxygen species leading to oxidative stress. However, this hypothesis has rarely been tested in free-ranging wild populations, where natural oxidative statuses and compensatory strategies may moderate immune responses and their impacts on oxidative status. Furthermore, the possibility that individuals scale their immune responses according to their oxidative status, conceivably to mitigate such costs, remains virtually unexplored. Here, we experimentally investigate the effects of a phytohaemagglutinin (PHA) immune-challenge on oxidative status in wild male and female white-browed sparrow weavers, Plocepasser mahali. We also establish whether baseline oxidative status prior to challenge predicts the scale of the immune responses. Contrary to previous work on captive animals, our findings suggest that PHA-induced immune-activation does not elicit oxidative stress. Compared with controls (n = 25 birds), PHA-injected birds (n = 27 birds) showed no evidence of a differential change in markers of oxidative damage or enzymatic and non-enzymatic antioxidant protection 24 hours after challenge. We did, however, find that the activity of a key antioxidant enzyme (superoxide dismutase, SOD) prior to immune-activation predicted the scale of the resulting swelling: birds with stronger initial SOD activity subsequently produced smaller swellings. Our findings (i) suggest that wild birds can mount immune responses without suffering from systemic oxidative stress, and (ii) lend support to biomedical evidence that baseline oxidative status can impact the scale of immune responses; a possibility not yet recognised in ecological studies of immunity.

Peer review as a quality assurance mechanism in three pharmacist-run medication-refill clinics

A peer-review system for monitoring pharmacists' practice in medication-refill clinics is described. Pharmacist practitioners trained in pharmacology, therapeutics, and physical assessment provide services in three medication-refill clinics associated with a 350-bed Department of Veterans Affairs (VA) medical center. The clinics serve patients who have exhausted their prescribed drugs before their next appointment with a physician. During a clinic visit, the pharmacist assesses the patient and the drug therapy and either consults an attending physician or writes new prescriptions. The pharmacist documents his or her activities in the medical record. The peer-review mechanism involves quarterly audits in which the chart notes written by the pharmacists are reviewed by other pharmacists. Five indicators of the quality of care are used in the peer reviews. The results are presented to the ambulatory-care and quality assurance pharmacy committees for analysis and discussion. The peer-review system has resulted in better compliance by the pharmacists with the quality indicators and clinic procedures, suggesting that the quality of care has also benefited. Peer review is used successfully to evaluate and monitor the care provided by pharmacists in medication-refill clinics associated with a VA medical center.

Respiratory syncytial virus infections on an adult medical ward

Eleven cases of respiratory syncytial virus (RSV) infection occurred in acutely ill hospitalized adults over a 7-week period. Nosocomial illness was suspected in two patients. Because RSV can cause serious infections in immunocompromised adults with the potential for nosocomial spread, the following recommendations are indicated: (1) during the winter months, early recognition and diagnosis of RSV infections both in hospital staff and in patients should be encouraged; (2) infected hospital personnel should avoid patient contact when possible; (3) during outbreaks, careful attention must be paid to hand washing and gloving; and (4) a high level of vigilance for RSV infection should be maintained on units with immunocompromised patients. Increased awareness of the potential risks of RSV infection is needed on adult medical units.

A double-blind, vehicle-controlled study of clobetasol propionate 0.05% (Temovate) scalp application in the treatment of moderate to severe scalp psoriasis

The efficacy and safety of clobetasol propionate 0.05% scalp application was evaluated in 378 patients with moderate to severe scalp psoriasis in a double-blind vehicle-controlled parallel group study. After 2 weeks of twice-daily applications, 81% receiving active drug versus 22% receiving vehicle had clearing of 50% or greater. Complete clearing was seen in 26% with active drug and 1% with vehicle. Local side effects were primarily burning or stinging in 11% and 10% of patients treated on an active or a vehicle regimen, respectively. The morning cortisol levels of 168 patients were checked at baseline and again after 2 weeks of drug therapy. Subnormal morning plasma cortisol values were seen in 5% of the patients receiving active drug and in 5% receiving vehicle; 13% of those taking active drug versus 5% taking vehicle had a 50% or greater decrease in morning cortisol at the 2-week visit compared with baseline values. Clobetasol propionate 0.05% scalp application appears to be a safe and an effective treatment for scalp psoriasis.

The Goeckerman regimen in two psoriasis day care centers

Three hundred patients with severe psoriasis were treated with the Goeckerman regimen in two different day care centers. Each patient was personally evaluated and followed by us for a period of 1 year or longer in an effort to determine accurately clearing of the skin, side effects, and length of remission. The average duration of treatment to produce over 90% clearing of the skin was 18 days. Ninety percent of the patients remained clear for a minimum of 8 months, and 73% were clear for 1 year or longer. The average total body dosage of ultraviolet B (UVB) needed to clearing was 1.96 joules/cm2. Side effects were minimal, and there was no increase in skin cancer. The cost-effectiveness of the regimen in a day care center is comparable to psoralens and ultraviolet A (PUVA) therapy.

Psoriasis: current advances in etiology and treatment

Psoriasis is a disease of major importance, the cause of which is unknown and treatment often difficult. However, research worldwide has intensified, and we now have an increased understanding of the events that lead to the production of a psoriatic lesion. Newer treatments and the revival of old therapies have increased the success rate in the management of this difficult disease but have also opened up new concerns regarding the safety of these modalities. This is a review of the current research on the etiology and treatment of psoriasis.

A congenital ichthyosiform syndrome with deafness and keratitis

This is a report on two children with a syndrome characterized by an extensive congenital ichthyosiform eruption, neurosensory deafness, hypotrichosis, partial anhidrosis, and vascularization of the cornea. The facial involvement is distinctive. Other features are dystrophy of the nails and tight heel cords. Both children are of normal intelligence. The inheritance pattern is unknown.

A mechanobullous disease of the newborn. Bart's syndrome

A patient had a unique mechanobullous disease (Bart's syndrome). The characteristic congenital localized skin defects, trauma-induced erosions, and nail deformities are present. The inheritance pattern appears to be autosomal dominant but, as in this report, isolated cases have been recognized. In a review of the other mechanobullous diseases, Bart's syndrome appears to present a distinctive clinical picture and course and has a favorable prognosis. The progressive spontaneous improvement emphasizes the importance of early recognition and conservative treatment.

Two tris urea mercaptoethanol extractable polypeptides found uniquely in scales of patients with psoriasis

This study was designed to chemically characterize the principal structural proteins of psoriatic scales. Cornified cells were obtained from 40 patients with psoriasis, 21 patients with other scaly diseases, and 13 normal individuals. Cells were washed with Tris-HCl buffer and incubated in 8 M urea containing 2-mercaptoethanol (pH 9.0) at 30 degrees C for 7 hr. Extracted proteins were subjected to SDS polyacrylamide gel electrophoresis and protein patterns from normal and diseased scales were compared. The 67,000 dalton constituent of normal cornified cells could not be identified in protein from psoriatic scale and instead, a pair of polypeptides of approximately 54,000 and 57,000 daltons appeared. These extra bands were not found in protein extractions from other skin diseases, uninvolved skin of psoriasis patients, or normal skin. In order to analyze further normal and psoriatic scale proteins, the immunoreaction of rabbit antisera to human 67,000 dalton polypeptide with extracted psoriasis protein and with frozen biopsy sections, was studied using immunoprecipitation tests and indirect immunofluorescence microscopy. Both techniques demonstrated the existence of the 67,000 dalton protein in psoriasis, but as a minor component. These results indicate that additional unique urea mercaptoethanol soluble proteins are formed in psoriatic lesions, and this unusual protein synthesis may reflect the morphological changes in this disease.

Psoriasis: treatment with a tar gel

Crude coal tar has long been an effective and safe form of therapy for psoriasis. However, as compounded in an ointment base it has many objectional features and usually is limited to hospital use. A new tar gel has been studied which appears to equal the effectiveness of crude coal tar, is convenient to apply, and is cosmetically acceptable. This new tar preparation is a valuable addition to the therapy of psoriasis.

Psoriasis day care centers

With the rapidly mounting cost of medical care in hospitals, physicians must seek alternative forms of therapy for illnesses that could conceivably be treated by less confining methods. One appraoch to this problem is the Psoriasis Day Care Center, where psoriasis patients with extensive disease are treated during the day and allowed to return home at night. The advantages include reduced cost, accessibility for more patients, and superior therapeutic results. This day care center concept could be equally applicable to other diseases now routinely treated by complete hospitalization.

Life-threatening dermatoses

Four life-threatening dermatoses-Stevens-Johnson syndrome, toxic epidermal necrolysis, Kaposi's varicelliform eruption and purpura fulminans-are unique in their abrupt onset and rapid progress to death, but prompt diagnosis and proper therapy can often cure the condition or prevent undesirable sequelae. Since two of the four conditions can follow the use of a variety of drugs and all may be secondary to an infectious agent, any physician may encounter them in practice and should be aware of their seriousness.

Ultraviolet-induced acantholysis in pemphigus

Ultraviolet irradiation produced an acantholytic phenomenon in normal skin of seven patients with pemphigus foliaceus. In six of the seven patients, this reaction was manifested by a positive Nikolsky sign and was confirmed by biopsy in four. Friction alone, infrared irradiation, occlusive dressing, and a rubefacient failed to produce a similar reaction. The thermal burn in the skin of patients having pemphigus was of subepidermal type. Ultraviolet-induced acantholysis was inhibited by chloroquine phosphate, taken orally, in the two patients tested. Prednisone had no such effect. It is concluded that ultraviolet light is a major aggravating stimulus for pemphigus foliaceus.