Lactating Females Do Not Discriminate Between Their Own Young and Unrelated Pups in the Communally Breeding Rodent, Octodon degus

Females in numerous rodent species engage in communal nesting and breeding, in which they share one or more nests to rear their young. A potential cost of communal nesting and breeding is that mothers divert resources to unrelated offspring. One way mothers could avoid this cost is to recognize and favour their own young over unrelated offspring when allocating maternal effort. We assessed whether female degus (Octodon degus), a communally nesting and breeding caviomorph rodent, discriminate between their own and unrelated offspring during lactation. Female degus previously have been shown to distinguish between their own and unrelated pups when exposed to odours from both. We measured pup discrimination based on differences in the retrieval behaviour of females that were in early or intermediate lactation directed towards their own and unrelated offspring; offspring presented were of similar or different age. Before any event of pup retrieval, lactating females spent similar amounts of time and interacted to a similar extent with their own and unrelated pups. During pup retrieval, all lactating females transported both pups to the nest. Neither relatedness to pups, nor pup‐age differences, influenced the order in which pups were retrieved to the nest. Dams waited similar amounts of time before retrieving the first pup when the first transported young was their own or unrelated. Likewise, females waited similar amounts of time before retrieving the second pup when the pup transported first was their own or unrelated. The time between first and second pup transport events was longer when dams were in early when compared with intermediate lactation, but only when pups were of similar age. All experimental subjects nursed unrelated pups after they were retrieved. Collectively, our results do not support the hypothesis that communally breeding female degus use their recognition ability to discriminate against unrelated offspring in favour of their own young.     

Paternal behavior increases testosterone levels in offspring of the California mouse

Paternal care during early development influences pup survivorship in the monogamous and biparental California mouse, Peromyscus californicus. Moreover, paternal pup retrievals impact development of adult offspring aggression and the neuropeptide vasopressin, yet little is known about the underlying mechanisms of these developmental changes. Because testosterone can increase arginine vasopressin and aggression, we hypothesized that paternal pup retrievals increase testosterone levels in prepubertal male P. californicus pups. Male pups were assigned to one of three groups: hormonal baseline, nonretrieval control, or retrieval. On postnatal days 18-21, all pups and the mother were removed from the cage, and the focal male pup was placed either outside of the nest to elicit paternal retrievals (retrieval group) or in the nest to discourage paternal retrievals (nonretrieval group). Testosterone was elevated at 45-min, but not 90-min, post-manipulation in retrieved compared to nonretrieved pups. Moreover, there was a significant positive correlation between pup retrievals and testosterone in the 45-min group. This rapid testosterone rise in response to paternal retrievals may facilitate an increase in aggression and vasopressin in adult offspring. Therefore, this period of development previously viewed as hormonally quiescent may be more active in response to paternal behavior than previously thought.     

Preference for own versus conspecific pups by inbred and outbred rats

Communal care of young may occur when related females live in close proximity to each other. The degree of relatedness between females may affect discrimination of own from conspecific young. Retrieval tests were used to examine preference for own versus conspecific pups by inbred and outbred rats. Dams were given retrieval tests in a neutral arena every other day from day 1 through 10 postpartum. Outbred, but not inbred, dams showed a significant preference for their own pups. Outbred dams also retrieved pups more slowly than did inbred dams. Differences in the behavior of dams and/ or similarity of cues presented by pups may be responsible for the lack of preference for own pups shown by inbred dams. The results of this study suggest that indiscriminate care of young should occur when closely related females share a nest.     

Effect of preoptic region implants of dilute estradiol on the maternal behavior of ovariectomized, nulliparous rats

Estrogen implanted directly into the medial preoptic region of pregnant Charles River Sprague-Dawley rats hysterectomized and ovariectomized on Day 16 of gestation mimics the effects of systemic estrogen treatment at this time by reducing the latency to respond to foster pups with maternal behavior (Numan, Rosenblatt, and Komisaruk, 1977). The present report describes the pup-directed responses of ovariectomized, nulliparous Zivic-Miller Sprague-Dawley rats that received bilateral medial preoptic implants of either cholesterol (n = 11) or estradiol diluted 1:10 with cholesterol (n = 11). Two days after treatment these animals were housed with three foster pups: their responsivity to pups and quality of nests built were then assessed, at first hourly and then daily. Rats receiving intracranial estradiol required significantly shorter exposures to pups than did cholesterol-treated animals before initiating carrying and grouping of 3 dispersed pups in a maternal nest during a 15-min test. On other measures, however, the groups did not differ (e.g., proportion grouping pups overnight, time required to complete retrieval of pups to the nest, time required to rebuild a disrupted nest). Animals treated with cholesterol and animals with estradiol implants did not differ in uterine weight at the time of sacrifice, suggesting that estrogen did not leak, even from this well-vascularized implant site, into the circulation. Thus, as in the pregnant animal, the facilitating effects of estrogen on maternal behavior can be mediated through the medial preoptic region; however, the effects were evident only when a test requiring retrieval of several pups within an arbitrarily short interval was given.     

Impact of seed abundance on seed processing and dispersal by the red ant Myrmica rubra

1. Myrmecochory sensu stricto is an ant–plant mutualism in which non‐granivorous ants disperse plant diaspores after feeding on their nutrient‐rich seed appendage, the elaiosome. Phenological traits associated with the diaspore can influence the behaviour of ants and thus their ultimate efficiency as seed dispersers. 2. This study investigated how a contrasting availability of seeds (20 vs. 200 seeds) from the diplochorous Chelidonium majus (Papaveraceae, Linnaeus) plant species influences the behaviour of Myrmica rubra (Formicidae, Linnaeus) ants, from the retrieval of seeds until their dispersal outside the ant nest. 3. Regardless of seed abundance, the ants collected the first diaspores at similar rates. Then, seed retrieval sped up over time for large seed sources until satiation took place with only one‐third of the tested colonies wholly depleting abundant seed sources. 4. No active recruitment by trail‐laying ants was triggered, even to an abundant seed source 5. In both conditions of seed abundance, the majority of the diaspores retrieved inside the nest were discarded with the elaiosome removed and were dispersed at similar distances from the nest. 6. The paper concludes with a discussion of how the quantity of seeds released by a plant with a dual mode of dispersal can potentially influence the behaviour of ant dispersers and hence the dispersal efficiency derived from myrmecochory.     

Patterns of maternal behavior of rats genetically selected for opposite coping styles

Maternal behavior of Koltushi High- and Low-avoidance (KHA and KLA) rats strains was assessed over the prewealing period (days 6-21). Ten litters of each strain were observed during the light phase of the light/dark cycle. In a series of experiments, rat pups were taken from the maternal nest and placed into the opposite corner of the cage. The following parameters of the maternal behavior were recorded: the latency of the first contact with the pups, pup licking, latency of carrying/retrieval of the first pup back to the nest, time of returning to the nest of the whole litter, and mother's spontaneous behavior (grooming and locomotion time) over the course of 10 min of observation. KLA mothers stayed with their pups and took care of them more frequently than KHA mothers during the light phase of the circadian cycle. Time of self-grooming was significantly higher in KHA rats. The highest levels of self-grooming of mothers was registered on the first day of testing. The latency of the first coming to pups after their removal from the nest was lower in KHA rats, but they needed more time to returned all pups to the nest. The experimental evidence suggests that the KHA but not KLA rats with the active coping style and higher stress reactivity display disorders in maternal behavior in a novel situation.     

Isolation calls and retrieving behavior in laboratory and wild-derived golden hamsters—No sign for inbreeding depression

Isolated juvenile golden hamsters produce ultrasonic and audible vocalizations, so-called isolation calls, as a reaction to being separated from their mother and nest and their cooling down. Their aim is to stimulate mothers to search and retrieve the pups. In this work, the vocalization of juvenile laboratory (Zoh:GOHA; Institute of Zoology, Martin-Luther-University Halle-Wittenberg) and juvenile wild-derived golden hamsters (captured in northern Syria and southern Turkey) from birth up to the age of 18 days were digitally recorded, analyzed and compared using an ultrasonic microphone and the software Avisoft. Furthermore, the retrieving behavior of the mothers was observed and compared. The results showed that the number of isolation calls was age-specific and the structure of the calls was influenced by body temperature, body mass and sex of the pups. The age of the pups determined retrieval by the maternal golden hamsters; however these did not discriminate between their own pups or foreign pups. In spite of enormous genetic differences between wild-derived and laboratory golden hamsters, only minor differences between the strains were found.     

Neonatal anesthesia for studies of hamster parental behavior when infanticidal aggression is a possibility

Experiments involving investigation of the neuroendocrine basis for paternal care in rodents risk activation of aggressive behavior toward pups. To minimize pain and suffering during tests of parental responsiveness requiring retrieval of a displaced pup to its nest, a method of anesthetizing the pup was developed in Djungarian hamsters, Phodopus campbelli. A surgical plane of anesthesia, as measured by criteria, such as respiratory depression, loss of the pedal reflex, and failure to increase respiratory rate or to vocalize in response to handling, was achieved by use of intraperitoneal administration of a combination of ketamine and xylazine. Both parents (tested separately) expressed normal behavior toward anesthetized pups. In random order, a saline-injected or anesthetized pup was displaced from its nest in the home cage. There were no differences in pick-up or retrieval rates between saline and anesthetized pups for either parent. A third test using an unmanipulated pup confirmed that parental behavior was not reduced toward an anesthetized pup. However, if anesthetized pups were tested first among littermates, retrieval by males was less likely. This method will, therefore, underestimate retrieval behavior in males, but not females. Adult male hamsters that had never been parents also expressed expected behavior by attacking the pup in 45% of cases. This method provides an efficient and effective means of protecting pups while allowing adults to express a wide range of parental and infanticidal behaviors. It also has application in behavioral screening of transgenic strains toward unrelated young.     

Litter stimulus factors in maternal retrieval (Rattus rattus)

Maternal retrieval by rats was compared for sedated and control pups at 2, 5, 10, and 15 days of age. The control animals were retrieved more quickly than the experimentals only on day 5. The results were interpreted as demonstrating that stimuli of the pups determining maternal care have varying effects with age.     

Sex Differences in Retrieval Behavior by the Biparental Convict Cichlid

Biparental species occasionally demonstrate a division of roles in which parents perform sex-typical tasks, with females offering direct care and spending the majority of their time with the offspring while males are more indirect in their care, providing the majority of defense against potential brood predators. To examine the flexibility in the sex-typical roles shown by convict cichlids ( Amatitlania nigrofasciata ), we displaced non-swimming young at three different distances from the nest and then analyzed the retrieval behaviors of each parent. Retrieval of altricial young is a behavior commonly used to measure parental care in mammalian studies, but has rarely been used in other taxa. We found sex differences in retrieval behavior: on average, females retrieved young close to the nest and males retrieved young far from the nest. This difference in parental contribution suggests a division of labor with sex-specific roles. Sex differences may be due to proximity to young and/or apparent risk of offspring predation. Additionally, we found that latency to first retrieval and total time spent retrieving young remained consistent across the various displacement distances, suggesting that retrieval is an essential parental behavior. Additionally, we include observations of wriggler retrieval by parents in a natural population of Costa Rican convict cichlids.     

Maternal behavior deficits in nulliparous oxytocin knockout mice

The first observations of postpartum oxytocin knockout (OTKO) mice found no maternal behavior deficits. However, it is unclear how detailed those observations were. In this study, we compared maternal behavior exhibited by OTKO and wild-type (WT) nullipara toward six 2-4-day-old foster pups during test sessions conducted on 3 successive days. Each day, subjects were placed in a clean cage 30 min prior to introduction of pups which were deposited in a clump adjacent to the middle of a long wall of each test cage. Behavior was measured for 3.5 h after which pups and test subjects were returned to their home cages. On test days 1 and 3, a significantly smaller proportion of OTKO females retrieved pups to a corner of their cage. Also, significantly fewer pups were retrieved to corners by OTKO females. In contrast to most WTs, most OTKO females mothered pups in the center of the cage where they were initially deposited. Pup-licking frequencies were significantly lower in OTKO females. Their self-grooming frequencies also trended toward being lower. Latencies to retrieve and lick pups, latencies to and frequencies of still crouching over pups and proportion of time in nest did not differ between groups. Our findings suggest that OT stimulates a significant proportion of pup-licking in nulliparous mice, a situation similar to lactating rat mothers. Our results also indicate that OT may play a role in the motivation to retrieve pups to a more secure location.     

Maternal behavior,milk ejection,and plasma hormones in Hatano high- and low-avoidance rats

Hatano high- and low-avoidance (in a two-way active avoidance task) animals (HAA and LAA, respectively) were successfully selected from a Sprague-Dawley rat population. Pup growth of both strains was dependent on the maternal strain in a cross-fostering study. To determine whether there are strain-specific differences between HAA and LAA in maternal care, both strains of dams were subjected to a test battery as measured by nest building, home cage behavior, pup retrieval, and milk ejection tests. In addition, changes in plasma concentrations of lactotropic and corticotropic hormones such as prolactin, ACTH, and corticosterone were examined during lactation. The test battery indicated that the dams of both strains built good nests and spent an identical amount of time with their offspring. However, LAA dams showed a prolonged latency time for pup retrieval and often left pups outside the nest until the end of the test period. LAA dams also showed a decreased amount of milk ejection, whereas no strain differences were observed in milk ejection after oxytocin treatment. During lactation, a lesser increase in plasma concentrations of prolactin and a greater increase in ACTH were found in LAA dams. There were no differences between the two strains in plasma concentrations of corticosterone. These results clearly demonstrated decreases in maternal behavior and milk ejection in LAA as compared to HAA dams. The present results also suggest that maternal motivation and mechanisms responsible for maternal hormones related to suckling are involved in the degree of pup growth.     

Evidence for Resetting the Directional Component of Path Integration in the House Mouse (Mus musculus)

Path integration is the animal's running computation of its position relative to a starting point based on recording all displacements. This process is known to be prone to cumulative errors and hence must somehow be corrected with the help of local spatial cues. In the reported experiments, the relative role of local spatial cues at two target locations was appraised. These two targets were the peripheral box of a female house mouse (Mus musculus) and a central box from where she retrieved her pups over a distance of 50 cm. The experimental conditions required the mouse to navigate between the two targets solely by means of path integration. To find out whether the mice continued integrating at the two target locations, directional misinformation was fed into their path integrating system. Hence, passive rotation of 90° proved to be sufficient to decide unambiguously whether the mice were misdirected. Such experimental interference consistently documented ongoing path integration at the target location outside the residential nest. In contrast, the same interference when the mouse was in the residential nest documented discontinuation of path integration in most cases. It is inferred that mice, when departing from residential nests, initially direct themselves by means of local guiding stimuli.     

Sexual and maternal behaviour at the postpartum oestrus: The role of experience in time-sharing

The postpartum sexual and maternal behaviour of Norway rats (Rattus norvegicus) was observed in a seminatural habitat. Behavioural decision-making by the female was examined by disrupting the nest and newborn offspring during mating. In experiment 1, multiparous females responded to nest disruption with an increase in maternal behaviour that was largely restricted to the post-ejaculatory intervals. The temporal and frequency measures of copulation were largely unaffected, implicating behavioural time-sharing. In experiment 2, following nest disruption primiparous females did not switch efficiently between maternal and sexual behaviour, showed poor retrieval of pups, and returned to the nest during ejaculatory series. They did not display the characteristics of behavioural time-sharing, indicating that previous experience may play a role in the ability to time-share.     

林睡鼠幼鼠的活动规律和行为初步观察

本文通过红外线照相的方法,对发育期的林睡鼠幼鼠进行室内活动规律及行为观察,为充分了解林睡鼠越冬前的能量储备形式提供饲养参考。将鼠密度监测仪固定在饲养笼具上方,24h连续拍照,采集和分析6-9月年龄在10周内的幼鼠各种活动数据。结果显示：幼鼠一天中超过70%的时间都在窝内度过,大部分时间都蜷缩成一团少有动作;在窝外活动时间多在玩耍,如攀爬笼架。用于进食和饮水的时间不超过全天的2%。林睡鼠幼鼠主要活动时间在21:00-07:00,活动高峰在21:00-03:00之间。幼鼠出生3周后开始出窝活动,哺乳期30d后开始采食,5周后幼鼠有交配玩耍行为。随着日龄的增长,活动高峰从23：00提前到21：00,活动时间也逐渐延长,但9周龄后活动时间逐渐缩短,幼鼠的饮水进食时间与其活动的时间长短较为一致。10周体重可达成年体重的70%。研究表明,林睡鼠在夏秋季节基本是昼伏夜出动物。光照是影响其在外活动的重要因素之一。幼鼠6周后所需的饲料和水量大于成年林睡鼠,在此期间要注意饲料和水的补充。     

Components of early maternal environment affecting the predisposition to catalepsy

Reciprocal pup substitution (cross-fostering) in cataleptic GC (designated so by the initials of words "genetic" and "catalepsy") and control Wistar females resulted in attenuation of cataleptic predisposition in GC rats fostered by Wistar foster-mothers. The latter demonstrate a more intense maternal care than GC females. There was a significant negative correlation between the frequency of mother staying in nest and the duration of pinch-induced catalepsy in pups fostered by her. In the home-cage retrieval test, the females of the strains compared showed a significant dependence of the latencies of approach to, and retrieval of, pups on their own and the pups' genotype.     

Olfactory and Thermal Influences on Ultrasonic Vocalization During Development in Rodents

Ultrasounds are emitted by developing rodents, and changes withage in several parameters of vocalization have been reportedfor numerous myomorphs. In this paper I integrate with ultrasonicvocalization several behaviors which change during development.Included are studies controlling stimulation by olfactory, thermal,and tactile cues as well as detailed studies of specific responsessuch as movement, suckling, grooming, and huddling. Developmentis analyzed in well-known species, such as the rat (Rattus norvegicus),and in less familiar species, especially the pine vole (Microtuspinetorum). Lacking the capacity for physiological thermoregulation, altricialrodent pups with their mother use several behavioral strategieswhich facilitate thermoregulation. Inside the nest, pups adjustthe temperature by changing their huddling. The mother regulatesthe length of suckling bouts according to her body temperature.When a pup is removed from the warm nest, vocalizations of thepup can increase the likelihood of retrieval by the mother andthereby indirectly facilitate thermoregulation. In several species which have been studied, vocalization ratesare highest when pups begin to move into and out of nests andexhibit olfactory-directed movement. As olfactory preferencesbecome established and movement is coordinated, a decline invocalization appears in rat, mouse, hamster, spiny mouse, andpine vole. In the gerbil, however, the decline precedes competencein olfactory-directed movement. In the presence of home shavings, young rats emit low ratesof vocalization, while pine vole young emit calls at a highrate. This contrast may relate to the intensive attachment ofyoung pine voles to the mother in early life.     

Presence of the father and parental experience have differentiated effects on pup development in Mongolian gerbils (Meriones unguiculatus)

Conflicting data exist on the importance of the father and parental experience during development in rodents. The purpose of this study was to investigate the effects of these two variables on development in Mongolian gerbils. Forty pairs of males and females with a litter size of between 4 and 7 pups were used as subjects. Twenty couples had no experience in raising young. After the birth of their pups, four experimental groups were formed: (I) inexperienced mother and father; (II) inexperienced mother; (III) experienced mother and father and (IV) experienced mother. When the pups reached 10 days of age, pup and parental behavior was recorded in experimental sessions of 15 min on 11 consecutive days. Through the statistical analysis it was found that the presence of the father significantly increased the physical contact between pups and parents and that pups opened their eyes earlier in comparison to the groups without the father. On the other hand, parental experience had a significant influence on the behavior of the pups (locomotion inside and outside the nest, and self-grooming). The results of this study suggest that parental experience and the presence of the father have differentiated effects on development in Mongolian gerbils.     

Do sires and juvenile male mice (C57BL/6) contribute to the rearing of the offspring?

Copulation and/or cohabitation with a pregnant female facilitate paternal behavior in male mice. However, their contribution to the rearing of the offspring is still not well understood. Our aims were to investigate the behavior of sires toward own or alien pups; the immediate consequences of the presence of fathers on the offspring and the behavior of the mother; and whether the exposure of juvenile males to newborn siblings, in an overlapping litters context, facilitates paternal behavior in C57BL/6 mice. We found that sires behaved paternally toward alien pups at both postpartum days 3 and 7; did not affect the behavior of the mother (e.g., licking and grooming, retrieval behavior, time in the nest, and crouching postures); and reduced the time offspring stayed alone in the nest. The exposure to newborn siblings did not promote paternal behavior in juvenile males. Therefore, sires are more paternal than usually described in the literature for laboratory mice, suggesting a facultative role in the rearing of the offspring. However, juvenile male mice, in contrast to juvenile females, could be adapted to leave the nest earlier without major contribution to the offspring.