The immunological function of allosuckling

Young mammals are unable to mount an efficient immune response against invading pathogens. Until their immune system is mature mothers transmit to their young immunological compounds during lactation. Given that genetic and foster mothers can assume this protective role, we propose that young mammals may gain immunological benefits by suckling more than one nursing female, a behaviour referred to as "allosuckling". This hypothesis has so far not been considered as a potential explanation for the propensity of young mammals to suckle foster mothers. However, pathogen transmission through milk during allosuckling may reduce the immunological net benefit that young gain, and furthermore allosuckling may increase pathogen transmission between foster and genetic mothers implying costs of allosuckling for all participants. Here, we develop the immunological function of allosuckling hypothesis (IFA) as a potential explanation for intra-and interspecific variation in allosuckling frequency. We present published experimental evidence for the assumption that immunological benefits of allosuckling depend on the immunological status of the offspring, the foster and the genetic mothers. Finally, we give predictions arising from the IFA hypothesis and propose that the IFA may provide a new explanation as to why neonates suckle various females and why foster females often refuse to nurse nonoffspring.     

英国惠普斯耐德獐的育幼行为

1993年5-8月在英国惠普斯耐德野生动物园半自然条件下研究了獐（）的单亲育幼行为。描述了母幼獐建立关系,母獐的探访和育幼行为,授幼行为,舔犊行为以及母幼间距离等。研究结果表明,母獐昼夜间仅探访幼兽4-5次。初生獐寻找乳头时往往寻错位置,找向母獐的前胸和颈区。在幼獐出生后的早期,哺乳行为的启动是由母獐启动的,但幼獐一周龄后即为启动者。平均哺乳时段为48.2±10.2s.母獐的舔犊行为常与哺乳同时发生,舔犊的位置最常见于幼獐的头部（62.7%）,其次是肛殖区（13.9%）,再是背部（8.4%）,肋部（7.2%）,胸部（5.6%）和颈部（2.1%）。此外,还讨论了母兽对不同性别的幼獐的投资的差异及其生物学意义。     

Differences in fertility and suckling patterns between primiparous and multiparous rhesus mothers (Macaca mulatta)

Primiparous females gave birth around the same time as multiparous nonlactating females, and earlier than did multiparous lactating females. No differences in birth sex ratio were found between primiparous and multiparous females. During the breeding season following birth, primiparous mothers returned to oestrus later than did multiparous mothers, and while few primiparous mothers conceived successfully during that season, most multiparous mothers did. Primiparous females suckled their infants more frequently than did multiparous females at all ages; infants of primiparous females also made more nipple contacts per bout, and had shorter sucking bouts. When mothers came into oestrus, suckling frequency drastically increased for primiparous females, but not for multiparous females, magnifying the differences between the two groups. After the first oestrus, suckling frequency declined for all mothers, but multiparous mothers had consistently lower suckling frequencies than did primiparous mothers. The high suckling frequency, and numerous nipple contacts per bout, found among primiparous mothers are likely to be related to the low reproductive chances that these females faced during the breeding season. Multiparous mothers seemed to compensate for their low suckling frequency by lengthening the suckling bouts, and this suckling pattern did not hinder their reproduction. It is argued that primiparous mothers might have to suckle their infants more frequently because they can only produce milk at slow rates, being in this way forced into a reproductively inhibiting suckling pattern. However, the delay in subsequent reproduction could be ultimately advantageous for primiparous mothers if it enhanced infant survival, and allowed the mothers to regain physical condition before reproducing again.     

Milk intake and production curves and allosuckling in captive Iberian red deer, Cervus elaphus hispanicus

In two experiments, we compared milk intake (assessed by weighing calves before and after suckling) and milk production (by hand milking hinds) in Iberian red deer both when calves sucked their mothers together (group-suckling experiment) and when mother and offspring were isolated (isolation-suckling experiment). In both experiments, the general lactation curve for calves increased to a peak and then decreased (type I, standard lactation curve in mammals), whereas the curve for hinds decreased from the start (type II). However, in the experiment on group suckling, calves ingested 17.2% more milk than that produced by their mothers from weeks 6 to 20. In both isolation- and group-suckling experiments, hinds showed an overproduction of milk decreasing from weeks 1 to 5. This decreasing overproduction coincides with a similar trend in calf mortality reported in the literature and might thus be aimed at ensuring calves have sufficient nutrients when mortality is highest. In addition, allosuckling observations in the group-suckling experiment showed an inverse relationship between milk production and percentage of allosucking attempts. Allosucking attempts were also more frequent after the milk overproduction period. Both findings suggest that allosuckling is a response to compensate for a reduced maternal milk supply. Copyright 2000 The Association for the Study of Animal Behaviour.     

Pasture Quality Affects Juvenile Survival through Reduced Maternal Care in a Mountain‐Dwelling Ungulate

Lactation exerts heavy energetic and physiological costs to mothers, whilst determining early growth and survival of offspring. To mountain ungulates, access to high‐quality forage during nursing and weaning is crucial for reproductive success. We have evaluated the effects of pasture quality on suckling behaviour and winter survival of Apennine chamois Rupicapra pyrenaica ornata kids, across three areas. Areas A‐B (‘poor’ areas) were characterised by a reduced availability of nutritious forage, thus a lower diet quality for female chamois and kids; Area C (a ‘rich’ area) included a much greater availability of nutritious forage. In poor areas, pasture quality has been reduced by climatic and plant composition changes, as well as the presence of a herbivore competitor (red deer Cervus elaphus). In poor areas, we recorded a significantly (1) lower suckling success of chamois kids (number of suckling bouts/number of suck attempts); (2) lower frequency of suckling bouts (n. suckling bouts/kid/h); and (3) lower suckling intensity (suck duration/kid/h) in respect to the rich area. Conversely, frequencies of suckling rejections and those of suckling attempts (n. events/kid/h) were the lowest in the rich area. Winter survival of chamois kids was c. 2 times greater in the rich area (45%) than in poor areas (20–26%). In the poor areas, resource scarcity induced adult female chamois to decrease maternal cares and favour their own maintenance, ultimately affecting population dynamics through kid winter mortality.     

Chronoethologische Untersuchung zur Jungtierentwicklung beim Weißlippenhirsch (Cervus albirostris) im Tierpark Berlin

A group of eight (2.6) White-lipped deer (Cervus albirostris) and four (1.3) fawns, born in 2010, kept in Tierpark Berlin were observed with focal point at circadian behavioural pattern, mother-child-interaction and the ontogeny of behaviour.The circadian rhythm of the animals proved to be bimodal and in its activity periods clearly synchronized with daily routine in the zoo. The animals showed different types of behaviours concerning metabolism (47%), comfort and resting (25%), movement (11%) and other behaviour (17%). The parallels between the distribution of behaviour and spatial use during the day point to an obvious relevance of different shaped enclosure areas to the behaviour. Calves of White-lipped deer are considered to be typical hiders („Ablieger“). Initially the fawns entered the enclosure trough the fence four to five times a day, exclusively for suckling. Until the fourth week of life their distribution of behaviour and their daily rhythm were well-adjusted to that of the adults. Despite of an age difference up to 17 days, the hiding period of all four fawns ended more or less at the same point of time; in case of the oldest fawn after 6, in case of the youngest fawn already after 3½ weeks of life. This indicates a synchronisation of the ontogeny of behaviour between older fawns and younger ones living with each other. In the process of dietary change from milk to solid food this synchronization was also to be seen. During the first two weeks the fawns were almost exclusively in contact with their mothers, but with time the bonding between the four fawns got stronger. The young affect each other in their development of behaviour. Above-mentioned traits of weaning in mammals point to the onset of weaning in the observed animals at three to four weeks of live.All in all the behavioural development of White-lipped deer obviously depends on physiological needs and abilities as well as social environment.     

Mother-calf relationships and maternal investment in European bison<Emphasis Type="Italic">Bison bonasus</Emphasis>

Mother-young relationships, up to the third month of the calves’ life, were investigated in European bisonBison bonasus (Linnaeus, 1758) from Białowieża National Park breeding centres (Poland). During the first week, calves spent most of their time close to their mothers and were rarely seen in the vicinity of other group members. Highest suckling rate, most frequent vocal contact and agonistic behaviour of mothers towards intruders, were other characteristics of this period. Although being a forest species, European bison exhibit a following type of strategy for offspring protection, typical for ungulates living in open areas; no hiding phase was observed. Suckling rates were similar in calves of both sexes, however, the pattern of nursing was different: male calves suckled longer, but in rarer bouts than female calves. The mothers’ condition, reflected by their social rank, did not influence the suckling rate. No sex differences were recorded in other maternal activities or mother-calf distance. The presumption of a lack of sex-biased maternal investment in European bison is confirmed by the results of other research.     

Suckling time and fawn growth in fallow deer (Dama dama)

The total suckling time and the fawns' absolute increase in weight from birth to weaning were studied in a group of fallow deer over two consecutive calving seasons. The aim was to clarify the use of suckling time as a predictor of parental input in fallow deer. When all subjects from both years are taken into account, no positive relation between suckling time and growth was found. This was due to at least two important factors: (i) fawns to primiparous mothers sucked relatively longer, with no corresponding increase in weight, compared to multiparous mothers; and (ii) suckling time during the first two weeks after birth seems to be an inadequate measure of milk transfer.     

Suckling behavior of eland antelopes (Taurotragus spp.) under semi-captive and farm conditions

Mother–offspring interactions soon after parturition play a key role in the survival of mammals. We investigated the suckling behavior of semi-captive Western Derby eland (Taurotragus derbianus derbianus) in a 60-ha enclosure covered by dense savanna vegetation in Senegal and farmed Common eland (T. oryx) on an open 2-ha pasture in the Czech Republic. We hypothesized that the basic pattern of suckling bout duration and mother–offspring interactions would be similar between species, but would vary in response to the environmental conditions and breeding system. During three calving periods, we observed the suckling of 27 and 23 calves of Derby and Common elands, respectively, between the ages of 1–5 months, and the interactions between mother and calf before and during suckling. Suckling bout duration increased with the age of the calves for both elands. However, in Derby elands we recorded longer suckling bouts in male than female calves and shorter suckling bouts in primiparous mothers than multiparous ones; no differences were found in farmed Common elands. The animals’ active approach to mother–offspring contact, for example naso–anal contact, and initiation and termination of suckling, resulted in longer suckling bouts in Derby elands. The results suggest that Derby elands that range over a large enclosure with dense vegetation cover adjust their maternal behavior in compliance with potential predator risk, facing a trade-off between nursing and vigilant behavior in the wild. The suckling behavior of farmed elands, on the other hand, reflects the conditions of captivity without predators and with the small available area enabling permanent visual contact of animals.     

The Neuroendocrine Function of Allosuckling

In mammals, females occasionally nurse offspring that are not their own. The function of allosuckling for foster females remains puzzling given that lactation is energetically costly and augments the risk of pathogen transmission. Current hypotheses suggest that allosuckling is not adaptive resulting from misguided parental behaviour, females reciprocate by nursing each other's offspring, females nurse preferentially related offspring for inclusive fitness benefits, females involved in allosuckling events evacuate extra milk or improve their maternal skills. These hypotheses received only little empirical evidence, and a recent review suggested that they are not mutually exclusive and do not exclude alternatives. Based on the established fact that teat stimulation by neonates leads to an elevated production of prolactin, I develop the hypothesis called ‘neuroendocrine function of allosuckling’ (NFA). The hypothesis postulates that the nursing of alien offspring allows females to increase and/or maintain prolactin concentration in the case own offspring do not stimulate their teats enough. This neurohormone enhances immunocompetence, the immunological quality and the quantity of milk whilst reducing female's fertility. The NFA suggests that via teat stimulation by the genetic offspring, and if necessary by foster ones, females can optimally adjust prolactin concentration, as both hypo‐ and hyper‐prolactinaemia entail physiological and immunological costs. The hypothesis does not only provide an explanation as to why females may nurse alien offspring but is also useful to understand the consequences of allosuckling. Indeed, even if mothers do not nurse alien offspring to control their prolactin production, allosuckling will alter the concentration of this crucial neurohormone.     

Maternal behavior and early development of pampas deer (Ozotoceros bezoarticus) fawns in a semi-captive environment

Maternal–infant interaction and behaviors are adapted to reduce the risk of predation and increase the probability of survival of the species. We determined how mother–young encounters and communication change by the development of the fawn (locomotion and feeding) throughout lactation in pampas deer (Ozotocerus bezoarticus). We registered the behavior of mother–fawn dyads for the first 60 postnatal days. Our results revealed three main developmental stages in the fawn, hiding (~0–19 days), active (~20–39 days), and adult-like (~40–60 days). In the hiding stage, the fawn stayed hidden, closer to the mother, and spent less time active, the mothers vocalized more often than the fawn, licked the fawns intensively while nursing, and were responsible for initiating nursing. In the active stage, licking behavior and vocalizations of the mother decreased while the fawns ate solid food, initiated nursing bouts, and displayed bursts of running activity. Finally, in the adult-like stage, the fawn showed many signs of nutritional weaning, and similar patterns of activity to their mothers. However, the duration and frequency of nursing bouts were unchanged during the study. We described mother–fawn interaction in pampas deer for the first time, and found that increased running activity in fawns anticipates nutritional weaning. Our results also suggest that to adapt to the development of the fawn, mothers only modify the dynamics of interaction and encounters rather than the time invested in nursing, an activity that also plays a role in maintaining mother–young affiliation.     

Maternal investment and reproductive success in Chinese water deer

Among cervids, maternal investment, estimated as the amount of resources and care allocated to the offspring, was expected to be related to species body size. Therefore, maternal investment in a herd of captive Chinese water deer Hydropotes inermis, a relatively small species of cervid, was investigated over 3 years. Except during the lactation period, reproductive females spent about 2-fold more time resting than feeding. During lactation, the amount of time spent feeding increased highly (25.3 min/h during lactation vs 17.3 min/h during the gestation period). Females spent less than 30% of time in communal behaviours with offspring. They did not reject alien fawns during this care period. Frequency and duration of suckling events decreased exponentially from the second week onwards. More than 10% of suckling bouts were non-filial. Prenatal investment leads to a mean litter mass (about 12% of maternal mass) higher than in most cervid species. Postnatal investment in fawns represents a daily mass gain of ca. 85 g/d during the first 2 weeks, without any sexual difference. Female production, timing and synchrony of births and survival of fawns characterized reproductive success. Seventy percent of mature females gave birth, with a mean of 1.9 offspring per female. The sex ratio was even. Births were synchronous, 80% of births occurring in 25 days. In this herd, 0.74 fawn per female was successfully weaned and 0.56 fawn per female survived through their first year. Based on these results we conclude that reproductive strategy of Chinese water deer was efficient and characterized by mother-offspring relationships typical of hiders and high levels of pre- and postnatal investments. This strategy seems typical of small species of cervids without marked sexual dimorphism.[Current Zoology 55(2):102-110,2009].     

On the quantification of suckling intensity in primates

The inhibitory effect that suckling has on the reproductive function of primate mothers varies as a function of the intensity with which they are suckled. Here we present an easily computed index of one parameter of suckling intensity, namely the temporal patterning of suckling bouts. High intensity suckling is characterized by frequent nursing bouts demarcated by short interbout intervals. Therefore, our suckling index is based on the brevity of observed interbout intervals, more specifically the proportion of such intervals that fail to exceed a criterion length. The index is an appropriate means of making interspecific comparisons of the development of infant suckling and is well suited for application to field data that include interbout intervals that were not observed in their entirety. To demonstrate its utility, we apply the index to field data collected on the suckling behavior of free-ranging rhesus monkey (Macaca mulatta) infants in India. In this context, we demonstrate that, in rhesus, between-infant differences in suckling intensity manifest themselves early in the postpartum period and contribute to between-female differences in the timing of first mating postpartum. Am J Phys Anthropol 105:33–42, 1998. © 1998 Wiley-Liss, Inc.     

Nursing Synchronization and Milk Ejection Failure as Maternal Strategies to Reduce Allosuckling in Pair-Housed Sows (Sus scrofa domestica)

Non‐offspring nursing (allosuckling) is costly for lactating females. It is reasonable to assume, therefore, that mechanisms have evolved to control the frequency of allosuckling. It is suggested that the synchronization of nursing between females could be such a mechanism. The aim of this study was to investigate whether nursing synchronization is related to the timing of nursing behaviour of paired sows and the behaviour of alien piglets in relation to allosuckling. Specifically, we predicted that: (i) nursing synchronization will increase if there is a real risk of allosuckling compared with a situation where there is none, (ii) nursing synchronization indeed reduces allosuckling and, therefore, those nursings with allosuckling attempts will be less closely synchronized than those without allosuckling attempts and (iii) in non‐synchronized nursings, the sows will more often employ another strategy to reduce allosuckling, namely, they will make the nursings non‐nutritive by not releasing milk. Ten pairs of sows and their litters were used in this study. For each pair, the two sows were housed individually until their litters were weaned; however, their litters had access to both sows from day 11 post‐partum. The behaviour of the 10 pairs of sows with their litters was videotaped for 6 h on days 10, 11, 17 and 24 post‐partum. The frequency of allosuckling attempts, non‐nutritive nursings and allosuckling during milk ejection was analysed for every pair for every day of observation. The observed frequency of nursing synchronization was high. The median interval between the start of a nursing within one pair of sows was 32 s. The first prediction was supported as synchronization became significantly tighter when piglets were given the possibility to allosuckle on day 11 [Cochran–Mantel–Haenszel (CMH) statistics, p < 0.0001]. The second prediction was also supported; the nursings were less closely synchronized when there were allosuckling attempts (CMH statistics, p < 0.05). Of all nursings, 36% had an allosuckling attempt; however, only 17% resulted in real allosuckling. Evidence in favour of the third prediction was also found as non‐nutritive nursings were more frequent in non‐synchronized nursings (CMH statistics, p < 0.05). Finally, real allosuckling during milk ejection was unrelated to the degree of nursing synchronization, as in less synchronized nursings, the sows responded to allosuckling attempts by not releasing milk. Our results suggest that sows are not able to completely suppress allosuckling; however, they can reduce its frequency through nursing synchronization and non‐nutritive nursings.     

Early growth in male and female fallow deer fawns

In this paper we present data from a long-term study on earlygrowth and related variables in fallow deer fawns living inlarge enclosures. Pre-winter body mass was constantly higherand more strongly correlated to subadult body mass in malesthan in females. To find out the mechanism for this higher pre-wintermass in males, we analyzed the variation in pre-winter massin relation to sex, year, mother's body mass, age and parityof mother, birth date, birth mass, growth rate, suckling behavior,and other behaviors. Birth mass was higher for male fawns, andgestation length, birth date, and weaning date did not differbetween the sexes. Consequently, both pre- and postnatal growthwere faster in males than in females. No behavioral differenceswere found between the sexes that could explain the differencein postnatal growth. Pre-winter mass was positively relatedto mother's body mass. Heavy mothers gave birth earlier andto larger offspring who grew at a higher rate, independent ofoffspring sex. However, male fawns born to primiparous mothershad relatively lower growth than male fawns born to multiparousmothers. This was not the case for female fawns. Suckling timeafter the first 2 weeks was positively related to mother's bodymass and growth of offspring. However, no measurements of sucklingbehavior differed between male and female fawns. Our results,except for the effect of parity on male and female growth, indicatethat selection has not acted on mothers to promote faster earlygrowth in males.     

Effect of age of calf on suckling behaviour and other behavioural activities of Zebu and crossbred calves during restricted suckling periods

The objective of this study was to investigate the effect of age of calf on the behaviour of Zebu and crossbred calves during restricted suckling (RS) periods. The behaviours of 20 Zebu and 16 crossbred calves were recorded during two 30-min sessions each day after milking when the calves and their dams were brought together in a group for suckling. This was made for a time period of 2 weeks/month for 6 months postpartum.The total suckling duration was significantly longer in Zebu calves (11.8+/-0.19 min) compared to the crossbred calves (9.4+/-0.19 min), but decreased significantly in both breeds with increasing age from 1 to 6 months. The number of suckling bouts decreased from a mean of 3.8 at 1 month of age to 1.1 at 6 month (P<0.05). The duration of each suckling bout decreased significantly from a mean of 3.5+/-0.15 min at 1 month of age to 1.6+/-0.01 min at 6 months (<0.05). The frequency of crossbred calves cross-suckling (3.7%) was significantly higher than that of the Zebu calves (1.9%; P<0.05). The frequency of calves cross-suckling decreased significantly from 4.2% at 1 month of age to 2.3% at 6 months. The duration and number of bouts of cross-suckling was significantly higher in the crossbred calves (duration 0.9+/-0.06 min; bouts 3, 7) than in the Zebu calves (duration 0.5+/-0.06 min; bouts 2, 7) and decreased with increasing age of calf. The duration and number of bouts of inter-sucking was significantly higher in the crossbred calves (duration 0.6+/-0.07 min; bouts 1, 6) than in the Zebu calves (duration 0.1+/-0.04 min; bouts 0, 5) and decreased with increasing age of calf. Exploration increased in duration as the calves increased in age from 1 to 6 months (P<0.05). The duration of play increased significantly with the increase in age of calf from 1 to 6 months, and occurred mainly after nursing.     

Suckling behaviour and fertility in rhesus macaques (Macaca multatta)

Lactation has been proposed as the main proximate mechanism regulating female fertility among non–seasonally breeding mammals. Less is known about the effects of lactation upon fertility among seasonal species, where photoperiodic control of reproduction is widely believed to have an overriding influence. In neither case is it clear which of the different components of lactation influence fertility and in which ways. In this paper, the links between suckling patterns and the likelihood of conception during the following breeding season are examined. Data were collected at the Madingley rhesus colony, where reproduction is strictly seasonal. It is shown that fertility was depressed in lactating females when compared to non–lactating ones. Within the lactating group, mothers who suckled their infants frequently, and with a great number of independent nipple contacts in each bout, failed to conceive during the following breeding season. It is suggested that early differences in suckling patterns might reflect differences in maternal condition; and that differences during the breeding season may affect the quality of the ovulations. A considerable decrease in both the frequency of suckling and the number of nipple contacts per bout seemed to be required for conception to occur. On the other hand, neither the duration of the suckling bouts, nor the duration of the intervals between bouts, were found to be associated with the likelihood of conception.     

Litter Size Determines Circadian Periodicity of Nursing in Rabbits

Nursing in rabbits occurs inside the nest with circadian periodicity. To determine the contribution of suckling stimulation in regulating such periodicity, we varied the size of the litters provided (1, 2, 4, or 6–8 pups). Nursing does, kept under a 14:10 (L:D) photoperiod, were continuously videotaped from parturition into lactation day 15. Although parturitions occurred throughout the day, a significant negative linear correlation (p?<?0.0001; r?=??0.68) was evident between time of delivery and time of nursing on lactation day 1, regardless of newborn number: longer intervals between these two events were seen in does delivering in the early morning than in those that gave birth late in the day. In rabbits suckling 6–8 pups, a Rayleigh analysis revealed that the population vector best describing their nursing pattern (across lactation days 1–15) had a phase angle?=?58° (corresponding to solar time 0352?h and rho?=?0.78; p?<?0.001). In contrast, the nursing pattern of does nursing litters smaller than 6 pups did not show circadian periodicity; rather, mothers showed multiple entrances into the nest box throughout the day. Cluster analysis revealed that the main equilibrium point of intervals between suckling bouts shifted from 24?h (6–8 pups) to 6?h (4 and 2 pups) and to as low as 4?h with 1 pup. In the groups nursing 2, 4, or 6–8 pups, most nursing episodes were followed by food and water intake. Those mothers also showed self-grooming of the ventrum and nipples after nursing. The incidence of these behaviors was lower in does nursing 1 pup. In conclusion, nursing in rabbits spontaneously occurs with circadian periodicity, but it is largely modulated by a threshold of suckling stimulation. (Author correspondence: gabygmm@gmail.com)     

Effects of chronic wasting disease on reproduction and fawn harvest vulnerability in Wisconsin white-tailed deer

Chronic wasting disease (CWD) is a fatal, transmissible spongiform encephalopathy that affects free-ranging and captive North American cervids. Although the impacts of CWD on cervid survival have been documented, little is known about the disease impacts on reproduction and recruitment. We used genetic methods and harvest data (2002-04) to reconstruct parentage for a cohort of white-tailed deer (Odocoileus virginianus) fawns born in spring 2002 and evaluate the effects of CWD infection on reproduction and fawn harvest vulnerability. There was no difference between CWD-positive and CWD-negative male deer in the probability of being a parent. However, CWD-positive females were more likely to be parents than CWD-negative females. Because our results are based on harvested animals, we evaluated the hypothesis that higher parentage rates occurred because fawns with CWD-positive mothers were more vulnerable to harvest. Male fawns with CWD-positive mothers were harvested earlier (>1 mo relative to their mother's date of harvest) and farther away from their mothers than male fawns with CWD-negative mothers. Male fawns with CWD-positive mothers were also harvested much earlier and farther away than female fawns from CWD-positive mothers. Most female fawns (86%) with CWD-positive mothers were harvested from the same section as their mothers, while almost half of male and female fawns with CWD-negative mothers were farther away. We conclude that preclinical stages of CWD infection do not prohibit white-tailed deer from successfully reproducing. However, apparently higher harvest vulnerability of male fawns with CWD-positive mothers suggests that CWD infection may make females less capable of providing adequate parental care to ensure the survival and recruitment of their fawns.     

Evaluation of the importance of roe deer fawns in the spring–summer diet of red foxes in southeastern Norway

Red fox Vulpes vulpes predation on roe deer Capreolus capreolus fawns has the potential to strongly affect prey population dynamics, but it is unclear whether this relationship is symmetrical or not. We analysed the spring–summer diet of adult foxes and of their cubs in a fragmented agricultural area of southeastern Norway, where a parallel study showed that the predator kills annually 25% of the radio-monitored roe deer fawns. The overall diet was highly varied and was dominated by small mammals (33% volume), especially Microtus agrestis, and medium-large mammals (25%), largely represented by fawns. The frequency of occurrence (FO) of fawns in the diet of adult foxes was highest in early spring, thus, supporting previous studies showing that the predator started actively hunting for fawns from the very beginning of the birth season. During the summer, the FO of both fawns and small mammals markedly declined, while that of berries and invertebrates increased. As expected for central-place foragers, cubs consumed a higher proportion of large prey items compared to adults. In particular, 25% of scats from cubs—versus 9% from adults—contained roe deer remains, suggesting a high profitability of fawns for vixens raising offspring. However, considering the wide food spectrum and the availability of several large prey items in our study area, it seems unlikely that the importance of fawns to the diet and population dynamics of red foxes could be as great as the impact of the predator on roe deer populations. This asymmetrical relationship implies that there are unlikely to be any stabilising feedback mechanisms in the predator–prey relationship.