Biological and behavioral predictors of relative energy intake after acute exercise.

Energy intake in the post-exercise state is highly variable and compensatory eating - i.e., (over-) compensation of the expended energy via increased post-exercise energy intake - occurs in some individuals but not others. We aimed to identify predictors of post-exercise energy intake and compensation. In a randomized crossover design, 57 healthy participants (21.7 [SD = 2.5] years; 23.7 [SD = 2.3] kg/m2, 75% White, 54% female) completed two laboratory-based test-meals following (1) 45-min exercise and (2) 45-min rest (control). We assessed associations between biological (sex, body composition, appetite hormones) and behavioral (habitual exercise via prospective exercise log, eating behavior traits) characteristics at baseline and total energy intake, relative energy intake (intake - exercise expenditure), and the difference between post-exercise and post-rest intake. We found a differential impact of biological and behavioral characteristics on total post-exercise energy intake in men and women. In men, only fasting (baseline) concentrations of appetite-regulating hormones (peptide YY [PYY, ß = 0.88, P < 0.001] and adiponectin [ß = 0.66, P = 0.005] predicted total post-exercise energy intake, while in women, only habitual exercise (ß = -0.44, P = 0.017) predicted total post-exercise energy intake. Predictors of relative intake were almost identical to those of total intake. The difference in energy intake between exercise and rest was associated with VO2peak (ß = -0.45, P = 0.020), fasting PYY (ß = 0.53, P = 0.036), and fasting adiponectin (ß = 0.57, P = 0.021) in men but not women (all P > 0.51). Our results show that biological and behavioral characteristics differentially affect total and relative post-exercise energy intake in men and women. This may help identify individuals who are more likely to compensate for the energy expended in exercise. Targeted countermeasures to prevent compensatory energy intake after exercise should take the demonstrated sex differences into account.

Quantifying snowfall from orographic cloud seeding.

Climate change and population growth have increased demand for water in arid regions. For over half a century, cloud seeding has been evaluated as a technology to increase water supply; statistical approaches have compared seeded to nonseeded events through precipitation gauge analyses. Here, a physically based approach to quantify snowfall from cloud seeding in mountain cloud systems is presented. Areas of precipitation unambiguously attributed to cloud seeding are isolated from natural precipitation (<1 mm h-1). Spatial and temporal evolution of precipitation generated by cloud seeding is then quantified using radar observations and snow gauge measurements. This study uses the approach of combining radar technology and precipitation gauge measurements to quantify the spatial and temporal evolution of snowfall generated from glaciogenic cloud seeding of winter mountain cloud systems and its spatial and temporal evolution. The results represent a critical step toward quantifying cloud seeding impact. For the cases presented, precipitation gauges measured increases between 0.05 and 0.3 mm as precipitation generated by cloud seeding passed over the instruments. The total amount of water generated by cloud seeding ranged from 1.2 × 105 m3 (100 ac ft) for 20 min of cloud seeding, 2.4 × 105 m3 (196 ac ft) for 86 min of seeding to 3.4 x 105 m3 (275 ac ft) for 24 min of cloud seeding.

An approach for studying the contributions of childhood sexual abuse and HPA axis dysregulation to substance use disorders.

An environmental risk factor for substance abuse and dependence is childhood sexual abuse (CSA). We piloted an approach we developed to test the hypothesis that hypothalamic-pituitary-adrenal (HPA) axis dysregulation from the stress of CSA is a biological mediator. We based our hypothesis on the allostasis model. New admissions to residential treatment for substance use disorders (N = 41) were evaluated for CSA history and two HPA axis regulation measures at baseline, one month, and two months. The two HPA axis regulation measures were morning cortisol level and the dexamethasone suppression test. Five potential covariates were also measured to increase reliability of the findings. Feasibility outcomes were mostly favorable, and included rates of participation (57 %), attrition (46 % at one month and 71 % at two months), and compliance with data collection procedures (87 % for morning cortisol level and 84 % for the dexamethasone suppression test). High attrition rates at one and two months were entirely attributable to high rates of leaving treatment, an important consideration for future studies. Baseline correlations among variables showed a significant negative correlation between dexamethasone suppression and perceived stress, a potential covariate (rho = -0.458). This finding suggests that individuals with lower stress levels have better negative feedback regulation of the HPA axis, which results in the benefit of lower cortisol exposure-a finding congruent with the allostasis model.

Social Support Buffers the Effects of Prenatal Depressed Mood: A Mixed-Methods Study.

BACKGROUND: Women use various coping strategies to deal with stress and depression. These strategies are shaped by social contexts over the life course and may attenuate and/or exacerbate the physiologic effects of depression. AIMS: The purpose of this study was to determine whether coping strategies (active, disengaged, or social support coping) moderate depression-related diurnal cortisol dysregulation and to explore how social context influences women's use of coping. METHODS: This was a mixed-methods study of pregnant women (N = 65) during mid-pregnancy. Cortisol was measured in saliva collected during the waking hours of the day. Participants completed the Edinburgh Depression Scale and the Brief COPE. A subset of the sample participated in semistructured qualitative interviews (n = 20). RESULTS: Social support coping, but not active or disengaged coping, moderated end-of-day cortisol levels. Among depressed women, higher use of social support was associated with lower and more dynamic (i.e., less flat) diurnal cortisol rhythms. The qualitative findings revealed how complex social dynamics related to financial insecurity, lack of mutuality, and social identity affected women's use of and access to social support. CONCLUSION: These findings support theories of the stress-buffering effects of social support. Future research is needed to examine how social determinants affect access to social support, and how early life social experiences condition women's adaptive formation of social support coping strategies over the life course. Clinically, these findings underscore the value of relationship-centered nursing care for depressed women.

Precipitation formation from orographic cloud seeding.

Throughout the western United States and other semiarid mountainous regions across the globe, water supplies are fed primarily through the melting of snowpack. Growing populations place higher demands on water, while warmer winters and earlier springs reduce its supply. Water managers are tantalized by the prospect of cloud seeding as a way to increase winter snowfall, thereby shifting the balance between water supply and demand. Little direct scientific evidence exists that confirms even the basic physical hypothesis upon which cloud seeding relies. The intent of glaciogenic seeding of orographic clouds is to introduce aerosol into a cloud to alter the natural development of cloud particles and enhance wintertime precipitation in a targeted region. The hypothesized chain of events begins with the introduction of silver iodide aerosol into cloud regions containing supercooled liquid water, leading to the nucleation of ice crystals, followed by ice particle growth to sizes sufficiently large such that snow falls to the ground. Despite numerous experiments spanning several decades, no direct observations of this process exist. Here, measurements from radars and aircraft-mounted cloud physics probes are presented that together show the initiation, growth, and fallout to the mountain surface of ice crystals resulting from glaciogenic seeding. These data, by themselves, do not address the question of cloud seeding efficacy, but rather form a critical set of observations necessary for such investigations. These observations are unambiguous and provide details of the physical chain of events following the introduction of glaciogenic cloud seeding aerosol into supercooled liquid orographic clouds.

Early life adversity and depressive symptoms predict cortisol in pregnancy.

Evidence suggests that exposure to early life adversity (ELA) programs the hypothalamic-pituitary-adrenal (HPA) axis to influence responses to later adversity and predisposes women to depression. However, few studies have examined whether ELA moderates the HPA cortisol response to adulthood adversity and depressive symptoms in pregnant women. The aims of this study were to determine (a) whether ELA, adulthood adversity, and depressive symptoms differentially predict patterns of cortisol and (b) whether ELA moderates the relationship of adulthood adversity or depressive symptoms to cortisol. This was a descriptive, cross-sectional study of pregnant women (N = 58, mean = 26.5 weeks gestation). Participants completed the Stress and Adversity Inventory and Edinburgh Depression Scale and collected salivary cortisol five times per day for 3 days to assess cortisol awakening response (CAR), diurnal cortisol slope, and cortisol area under the curve (AUC). ELA predicted a larger CAR, while depressive symptoms predicted a blunted CAR and higher cortisol AUC. Adulthood adversity predicted a blunted CAR and steeper diurnal slope, but only in women with high ELA. ELA also moderated the effect of depressive symptoms on diurnal slope. Early adversity and depressive symptoms appear to have significant effects on the HPA axis during pregnancy, with early adversity also moderating effects of depressive symptoms and adulthood adversity on cortisol regulation. Early adversity may be an important factor in identifying unique HPA phenotypes and risk for HPA axis dysregulation in pregnancy.

Vasopressin, but not oxytocin, modulates responses to infant stimuli in marmosets providing care to dependent infants.

In family-living species, the quality and patterning of caregiving is the product of an individual's role within the family (mother, father, sibling) and parental experience, both of which interact with underlying neurobiological substrates. Among these substrates are the nonapeptides vasopressin and oxytocin, which modulate maternal, paternal, and alloparental care. We used a nonhuman primate model of the "nuclear family," the marmoset (Callithrix jacchus), to investigate relationships between caregiving experience, role within the family, and activation of either the oxytocin or vasopressin systems in shaping responsiveness to offspring. During two phases of offspring development (early infancy, juvenile), mothers, fathers, and older siblings were treated with vasopressin, oxytocin, or saline via intranasal application, and tested for responses to infant distress stimuli in a within-subjects design. Interest in infant stimuli was highest among marmosets that were caring for infants compared to those caring for juveniles, and parentally experienced marmosets were quicker to respond to infant stimuli than first-time caregivers. Moreover, marmosets treated with vasopressin showed enhanced responsiveness to infant stimuli compared to control stimuli only when caring for infants. Thus, in all classes of marmoset caregivers, vasopressin enhances responsiveness to infant-associated stimuli in caregivers during periods in which infant care is most crucial.

A Comparison of the Ability of Leu8- and Pro8-Oxytocin to Regulate Intracellular Ca2+ and Ca2+-Activated K+ Channels at Human and Marmoset Oxytocin Receptors.

The neurohypophyseal hormone oxytocin (OT) regulates biologic functions in both peripheral tissues and the central nervous system. In the central nervous system, OT influences social processes, including peer relationships, maternal-infant bonding, and affiliative social relationships. In mammals, the nonapeptide OT structure is highly conserved with leucine in the eighth position (Leu8-OT). In marmosets (Callithrix), a nonsynonymous nucleotide substitution in the OXT gene codes for proline in the eighth residue position (Pro8-OT). OT binds to its cognate G protein-coupled receptor (OTR) and exerts diverse effects, including stimulation (Gs) or inhibition (Gi/o) of adenylyl cyclase, stimulation of potassium channel currents (Gi), and activation of phospholipase C (Gq). Chinese hamster ovary cells expressing marmoset or human oxytocin receptors (mOTRs or hOTRs, respectively) were used to characterize OT signaling. At the mOTR, Pro8-OT was more efficacious than Leu8-OT in measures of Gq activation, with both peptides displaying subnanomolar potencies. At the hOTR, neither the potency nor efficacy of Pro8-OT and Leu8-OT differed with respect to Gq signaling. In both mOTR- and hOTR-expressing cells, Leu8-OT was more potent and modestly more efficacious than Pro8-OT in inducing hyperpolarization. In mOTR cells, Leu8-OT-induced hyperpolarization was modestly inhibited by pretreatment with pertussis toxin (PTX), consistent with a minor role for Gi/o activation; however, the Pro8-OT response in mOTR and hOTR cells was PTX insensitive. These findings are consistent with membrane hyperpolarization being largely mediated by a Gq signaling mechanism leading to Ca2+-dependent activation of K+ channels. Evaluation of the influence of apamin, charybdotoxin, paxilline, and TRAM-34 demonstrated involvement of both intermediate and large conductance Ca2+-activated K+ channels.

Binding Characteristics of Two Oxytocin Variants and Vasopressin at Oxytocin Receptors from Four Primate Species with Different Social Behavior Patterns.

A clade of New World monkeys (NWMs) exhibits considerable diversity in both oxytocin (OT) ligand and oxytocin receptor (OTR) structure. Most notable is the variant Pro8-OT, with proline instead of leucine at the eighth position, resulting in a rigid bend in the peptide backbone. A higher proportion of species that express Pro8-OT also engage in biparental care and social monogamy. When marmosets (genus Callithrix), a biparental and monogamous Pro8-OT NWM species, are administered the ancestral Leu8-OT, there is no change in social behavior compared with saline treatment. However, when Pro8-OT is administered, marmosets' sociosexual and prosocial behaviors are altered. The studies here tested the hypothesis that OTR binding affinities and OT-induced intracellular Ca2+ potencies would favor the native OT ligand in OTRs from four primate species, each representing a unique combination of ancestral lineage, breeding system, and native OT ligand: humans (Leu8-OT, monogamous, apes), macaques (Leu8-OT, nonmonogamous, Old World monkey), marmosets (Pro8-OT, monogamous, NWM), and titi monkeys (Leu8-OT, monogamous, NWM). OTRs were expressed in immortalized Chinese hamster ovary cells and tested for intact-cell binding affinities for Pro8-OT, Leu8-OT, and arginine vasopressin (AVP), as well as intracellular Ca2+ signaling after stimulation with Pro8-OT, Leu8-OT, and AVP. Contrary to our hypothesis, Pro8-OT bound at modestly higher affinities and stimulated calcium signaling at modestly higher potencies compared with Leu8-OT in all four primate OTRs. Thus, differences downstream from a ligand-receptor binding event are more likely to explain the different behavioral responses to these two ligands.

Oxytocin modulates mate-guarding behavior in marmoset monkeys.

In socially-monogamous species, intolerance of interactions between a pairmate and a sexual rival (i.e., mate-guarding) promotes the preservation of long-lasting partnerships. One promising neurobiological candidate for the regulation of mate-guarding behavior in monogamous primates is the oxytocin (OT) system, given its established role in both the development of monogamous bonds and the behavioral processes that facilitate the preservation of those bonds. In this study, male and female marmosets were exposed to a same-sex intruder in their home environment during conditions when their pairmate was present and absent, and across three treatment conditions (OT receptor agonist; saline control; OT receptor antagonist). Saline-treated marmosets spent significantly more time in proximity to the intruder, relative to the empty pairmate enclosure, when their pairmate was absent. However, when marmosets received OT they spent less time in proximity to the intruder, indicating that OT may reduce interest in a same-sex stranger in a territorial context. When their pairmate was present, saline-treated marmosets spent equal time in proximity to both intruder and pairmate; yet when they received OT they spent significantly more time in proximity to the intruder, indicating that OT may increase interest in a same-sex stranger in a mate-guarding context. While OT treatment did not directly influence the expression of aggression, OT system manipulations impacted the expression of selective social interest during an intruder challenge, suggesting that OT may enhance adaptive responses to social challenges. Moreover, these findings add to the converging evidence that the OT system regulates behavioral processes that underlie the preservation of established relationships.

Oxytocin regulates reunion affiliation with a pairmate following social separation in marmosets.

While separation from significant social partners produces a host of neurobiological and behavioral perturbations, including behavioral distress and increased glucocorticoid production, positive social interactions upon reunion are critical for the reestablishment of normative relationship dynamics and the attenuation of the biobehavioral stress response. The hormone oxytocin has critical and pervasive roles in reproductive and behavioral processes across the lifespan, and plays a particularly prominent role in social bonding. In this study, we examined the extent that oxytocin modulates interactions with a pairmate following separation challenges that varied in both social context (isolation; separation) and duration (long; short), in marmosets. We demonstrated that the impact of pharmacological manipulations of the oxytocin system on the expression of affiliation upon reunion depended on both the context and duration of the separation challenge. Specifically, marmosets treated with an oxytocin antagonist spent less time in proximity with their pairmate upon reunion following a long-separation challenge. During the short-separation challenge, marmosets engaged in more social gaze when separated with an opposite-sex stranger, but not when separated with their mate. Furthermore, marmosets that received the most social gaze from opposite-sex strangers spent the most time in proximity with their long-term mate upon reunion. We also showed that marmosets treated with an OT agonist received increased levels of gaze from opposite-sex strangers, but not from their mate. Overall, these results suggest that marmosets are sensitive to the nature of the social interactions during separation, and subsequently alter their expression of affiliation upon reunion with their long-term mate. These findings further implicate oxytocin as a bond-enhancing molecule that regulates the reestablishment of normative levels of affiliation with a mate following separation, and add to the emerging literature that suggests the OT system underlies critical behavioral processes that contribute to the preservation of long-lasting social bonds.

Neuropeptide diversity and the regulation of social behavior in New World primates.

Oxytocin (OT) and vasopressin (AVP) are important hypothalamic neuropeptides that regulate peripheral physiology, and have emerged as important modulators of brain function, particularly in the social realm. OT structure and the genes that ultimately determine structure are highly conserved among diverse eutherian mammals, but recent discoveries have identified surprising variability in OT and peptide structure in New World monkeys (NWM), with five new OT variants identified to date. This review explores these new findings in light of comparative OT/AVP ligand evolution, documents coevolutionary changes in the oxytocin and vasopressin receptors (OTR and V1aR), and highlights the distribution of neuropeptidergic neurons and receptors in the primate brain. Finally, the behavioral consequences of OT and AVP in regulating NWM sociality are summarized, demonstrating important neuromodulatory effects of these compounds and OT ligand-specific influences in certain social domains.

Prenatal androgen exposure and parental care interact to influence timing of reproductive maturation in marmosets.

The timing of reproductive maturation is susceptible to hormonal and environmental influences, and variation in this timing can be partially attributed to the prenatal and post-natal environment. We examined associations between prenatal steroid exposure and the post-natal family environment on the variability in reproductive maturation timing in young marmosets (Callithrix geoffroyi). Urine samples from pregnant females were analyzed for cortisol (CORT) and androgens (uA). Post-natal uA was measured in males to determine age (in days) of adult-like levels of androgens associated with spermatogenesis; post-natal pregnanediol glucuronide (PdG) was measured in females to determine age (in days) of first ovulation. Maternal, paternal, alloparental, and total care (carrying, grooming, and rejection/removals) of offspring were observed. Female offspring exposed to lower prenatal uA levels and higher paternal grooming and lower maternal rejection/removals showed later first ovulation, whereas female offspring exposed to higher prenatal uA showed earlier first ovulation. Male offspring showed earlier reproductive maturation as paternal grooming increased, regardless of first trimester uA exposure. Male offspring exposed to low prenatal uA levels showed earlier reproductive maturation as maternal rejections/removals increased. In offspring exposed to low prenatal CORT, high total carrying predicted earlier first ovulation in females, but later reproductive maturation in males. Total carrying duration did not affect timing of reproductive maturation in offspring exposed to high third trimester CORT levels. Our findings expand the evolutionary theory of socialization by demonstrating that the effect of post-natal family environment on timing of reproductive maturation depends on prenatal uA exposure and also influences reproductive maturation timing in male offspring.

Neonatal oxytocin and vasopressin manipulation alter social behavior during the juvenile period in Mongolian gerbils.

Oxytocin and vasopressin are important modulators of a wide variety of social behaviors, and increasing evidence is showing that these neuropeptides are important organizational effectors of later-life behavior as well. We treated day-old gerbil pups with oxytocin, vasopressin, an oxytocin receptor antagonist, a vasopressin V1a receptor antagonist, or saline control, and then measured received parental responsiveness during the early postnatal period and juvenile social behavior during weaning. Neonatal vasopressin treatment enhanced sociality in males, but not females, at both developmental time points. When pups were individually placed outside the nest, parents were more responsive to male pups treated with vasopressin compared with littermates, and vasopressin treated male pups exhibited increased play with littermates as juveniles. These results show that vasopressin during very early life can enhance social interactions throughout early development.

Oxytocin and vasopressin enhance responsiveness to infant stimuli in adult marmosets.

The neuropeptides oxytocin (OT) and arginine-vasopressin (AVP) have been implicated in modulating sex-specific responses to offspring in a variety of uniparental and biparental rodent species. Despite the large body of research in rodents, the effects of these hormones in biparental primates are less understood. Marmoset monkeys (Callithrix jacchus) belong to a clade of primates with a high incidence of biparental care and also synthesize a structurally distinct variant of OT (proline instead of leucine at the 8th amino acid position; Pro(8)-OT). We examined the roles of the OT and AVP systems in the control of responses to infant stimuli in marmoset monkeys. We administered neuropeptide receptor agonists and antagonists to male and female marmosets, and then exposed them to visual and auditory infant-related and control stimuli. Intranasal Pro(8)-OT decreased latencies to respond to infant stimuli in males, and intranasal AVP decreased latencies to respond to infant stimuli in females. Our study is the first to demonstrate that Pro(8)-OT and AVP alter responsiveness to infant stimuli in a biparental New World monkey. Across species, the effects of OT and AVP on parental behavior appear to vary by species-typical caregiving responsibilities in males and females.

Do marmosets care to share? Oxytocin treatment reduces prosocial behavior toward strangers.

Cooperatively-breeding and socially-monogamous primates, like marmosets and humans, exhibit high levels of social tolerance and prosociality toward others. Oxytocin (OXT) generally facilitates prosocial behavior, but there is growing recognition that OXT modulation of prosocial behavior is shaped by the context of social interactions and by other motivational states such as arousal or anxiety. To determine whether prosociality varies based on social context, we evaluated whether marmoset donors (Callithrix penicillata) preferentially rewarded pairmates versus opposite-sex strangers in a prosocial food-sharing task. To examine potential links among OXT, stress systems, and prosociality, we evaluated whether pretrial cortisol levels in marmosets altered the impact of OXT on prosocial responses. Marmosets exhibited spontaneous prosociality toward others, but they did so preferentially toward strangers compared to their pairmates. When donor marmosets were treated with marmoset-specific Pro(8)-OXT, they exhibited reduced prosociality toward strangers compared to marmosets treated with saline or consensus-mammalian Leu(8)-OXT. When pretrial cortisol levels were lower, marmosets exhibited higher prosociality toward strangers. These findings demonstrate that while marmosets show spontaneous prosocial responses toward others, they do so preferentially toward opposite-sex strangers. Cooperative breeding may be associated with the expression of prosociality, but the existence of a pair-bond between marmoset partners appears to be neither necessary nor sufficient for the expression of spontaneous prosocial responses. Furthermore, high prosociality toward strangers is significantly reduced in marmosets treated with Pro(8)-OXT, suggesting that OXT does not universally enhance prosociality, but, rather OXT modulation of prosocial behavior varies depending on social context.

Pilot Study on Childhood Sexual Abuse, Diurnal Cortisol Secretion, and Weight Loss in Bariatric Surgery Patients.

Childhood sexual abuse increases risk for adult obesity. A potential contributing factor is altered cortisol secretion. In this pilot study, relationships among childhood sexual abuse, diurnal salivary cortisol secretion, and weight loss were explored in 17 bariatric surgery patients. Measurement points were before surgery (baseline) and 3 and 6 months after surgery. Childhood sexual abuse was measured by the Childhood Trauma Questionnaire. The results showed moderate but nonsignificant positive correlations between the childhood sexual abuse subscale score and baseline morning cortisol, evening cortisol, and daily mean cortisol. An unexpected positive correlation was noted between the Childhood Trauma Questionnaire total score and weight loss at six months. Diurnal cortisol secretion did not change over time after surgery nor correlate significantly with weight loss at six months.

Hybridization effects and genetic diversity of the common and black-tufted marmoset (Callithrix jacchus and Callithrix penicillata) mitochondrial control region.

Hybridization is continually documented in primates, but effects of natural and anthropogenic hybridization on biodiversity are still unclear and differentiating between these contexts remains challenging in regards to primate evolution and conservation. Here, we examine hybridization effects on the mitochondrial DNA (mtDNA) control region of Callithrix marmosets, which provide a unique glimpse into interspecific mating under distinct anthropogenic and natural conditions. DNA was sampled from 40 marmosets along a 50-km transect from a previously uncharacterized hybrid zone in NE Brazil between the ranges of Callithrix jacchus and Callithrix penicillata. DNA was also collected from 46 marmosets along a 30-km transect in a hybrid zone in Rio de Janeiro state, Brazil, where exotic marmosets appeared in the 1980s. Combining Callithrix DNA sampled inside and outside of these hybrid zones, phylogenetic and network analyses show C. jacchus and C. penicillata being parental species to sampled hybrids. We expand limited Callithrix population genetics work by describing mtDNA diversity and demographic history of these parental species. We show ancient population expansion in C. jacchus and historically constant population size in C. penicillata, with the latter being more genetically diverse than the former. The natural hybrid zone contained higher genetic diversity relative to the anthropogenic zone. While our data suggest hybrid swarm formation within the anthropogenic zone due to removed physical reproductive barriers, this pattern is not seen in the natural hybrid zone. These results suggest different genetic dynamics within natural and anthropogenic hybridization contexts that carry important implications for primate evolution and conservation.

Behavioral responses to social separation stressor change across development and are dynamically related to HPA activity in marmosets.

Psychosocial stressors activate two distinct stress-response systems, a central, behavioral response, and a peripheral, endocrine response. Both behavioral and endocrine responses to stressors are subject to individual and developmental variables, but it is not known whether stressor induced behaviors are stable across development, and how they correspond with changes in the endocrine component of the stress response. We characterized the development and stability of behavioral responses to a mild psychosocial stressor in marmosets (Callithrix geoffroyi), and assessed the degree to which the behavioral and endocrine stress-response systems were co-activated. The behavioral response to stressors was stable within individuals, but only some stressor-induced behaviors changed as the monkeys developed. Overall, there was more variability in the development of behavioral responses compared to stress-induced endocrine profiles found previously [French et al., 2012. Horm Behav 61:196-203]. In young marmosets, only increased alarm calling was correlated with increased cortisol reactivity, and in older marmosets increased cage manipulations and motor activity were associated with poorer post-stressor cortisol regulation. Because these relationships were so few, we conclude that while the behavioral and endocrine systems follow a similar developmental trajectory, each system maintains a level of independence. Furthermore, the relationship between stressor-induced behaviors and HPA activity changes across development.