Peromyscus Maniculatus Bairdi Research Articles

Density‐dependent predation of weed seeds in maize fields

Summary Seed predation can cause substantial losses of newly produced weed seeds and can therefore be important in regulating weed densities. The impact on weed population dynamics is greatest if predation acts in a directly density‐dependent manner. We investigated the effect of between‐patch variability in seed density on seed removal. For this purpose, artificial weed seed patches were created by broadcasting giant foxtail Setaria faberi, at low (1000 seeds m−2), medium (4500 seeds m−2) and high densities (9500 seeds m−2) over 25 ¥ 25 m areas within three maize fields in August. Changes in giant foxtail seed densities were evaluated 3 weeks and 7 weeks post‐application, using soil surface sampling. Observations of seed predation rate (seeds seed−1 week−1), using seed cards and exclosure cages, activity–densities of invertebrates using pitfall traps, and population estimates of rodents using Sherman live traps, were conducted to understand and explain the dynamics of seeds on the soil surface. Three weeks after seed addition, seed predation was strongly and inversely density dependent. After 7 weeks, the net response since the start of the experiment exhibited only a weak inverse density dependence. This means that between 3 weeks and 7 weeks after seed addition, the response had reversed from inverse to almost direct density dependence. During the August–October period, seeds in maize fields were mainly consumed by invertebrates. The most abundant granivorous invertebrates were crickets Gryllus pennsylvanicus and Allonemobius allardi, and carabid beetles, especially Harpalus pensylvanicus. The insects appeared unable to detect and respond numerically to weed patches, resulting in inversely density‐dependent predation, which favours the persistence of weed patches. The granivorous prairie deer mouse Peromyscus maniculatus bairdi, was present but contributed little to overall seed losses in autumn. Synthesis and applications. The results of this study indicate that weed densities in maize fields currently are not regulated through directly density‐dependent seed predation, because the time between seed shed and seed movement into soil is too short for invertebrates to respond to and level out spatial differences at the scale of weed patches. However, our results suggest that delaying crop harvest and tillage may provide invertebrate predators with more time to attack weed seeds, and may allow for subsequent predation by vertebrates, which would be directly density‐dependent.

Fostering house mice onto rats and deer mice: Effects on response to species odors

Newborn wild house mice (Mus musculus) were fostered upon maternal conspecifics, prairie deer mice (Peromyscus maniculatus bairdi) or laboratory rats (Rattus norvegicus). Male subjects were weaned into individual cages, in which they remained until testing commenced. At 35 days of age, subjects were given a four-choice test in which they had the opportunity to investigate tunnels scented with clean wood chips or with chips soiled by an adult male conspecific, deer mouse or rat. Compared to theMus-nursed andPeromyscus-nursed mice,Rattus-nursed mice were more active during the test and less reluctant to investigate theRattus-scented tunnel. These results were replicated in a two-choice test (Mus- vs.Rattus-scented tunnels) that included a group of mice fostered onto conspecifics, but withRattus scents present in the maternity cage throughout the nursing period. Early exposure to the scent ofRattus had no significant effects on the responses ofMus-nursed mice to the scent ofRattus.

Tests of preferences of adult deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Seven experiments were conducted to test the performance of adult deer mice (Peromyscus maniculatus bairdi) in discriminating and preferring siblings versus nonsiblings. In two experiments there was no indication of preferences based on odor alone. Further, there was no indication of kin discrimination in a seminatural enclosure. There was some indication that in a test apparatus, estrous females associate preferentially with male siblings rather than nonsiblings. The effect appears dependent on the presence of siblings during development. Although the finding of a preference for siblings in estrous females is counter to expectations from an inbreeding avoidance approach, this is one of a variety of findings to suggest that not all animals avoid inbreeding all of the time.

Tests of preferences of young deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Three experiments were conducted to test the performance of young deer mice (Peromyscus maniculatus bairdi) in associating preferentially with siblings versus nonsiblings. In Experiment 1, neither males nor females preferred caged siblings versus nonsiblings. In Experiment 2, with full contact permitted, nonsibling males were in contact as much as were sibling males. In Experiment 3, with pairs of littermate pairs permitted full contact, there was no significant differential association. Although discrimination and preferences related to kinship have been demonstrated in some species, they cannot be assumed to be universal.

Tests of preferences of young deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Tests of preferences of young deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Tests of preferences of adult deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Tests of preferences of adult deer mice (Peromyscus maniculatus bairdi) for siblings versus nonsiblings.

Mating capacity of male deer mice (Peromyscus maniculatus bairdi) copulating with successive females

Each of 30 male deer mice, Peromyscus maniculatus bairdi, was provided the opportunity to copulate with 3 successive females for 1 h each. Male capacity was limited; only 22 males copulated with all 3 females and only 11 ejaculated with all 3 females. The amount of copulation decreased with successive females. The numbers of females pregnant in the three ordinal positions were 18, 15, and 8, respectively. However, for the males that ejaculated with a female, there was no decrease in potency across successive females; the decreases that did occur overall were due to males that did not mate. For deer mice, unlike other species, even relatively sensitive methods reveal that males cease copulating before marked decreases in the potency of their ejaculates develop.

Sperm competition in deer mice (Peromyscus maniculatus bairdi)

Six experiments were conducted to determine the effects of mode of estrus (cycling versus postpartum) and intervals between matings on sperm competition in deer mice. When there was no lengthy interval between matings by different males, sperm competition matings by different males, sperm competition with females in postpartum estrus was the same as that with females in cyclin estrus (i.e., no male order effect). Imposition of 4 h delays between males did not engender a mating advantage when females were in postpartum estrus. When 4 h intervals were imposed with females in cycling estrus and tests were begun relatively early in the dark phase, there was a secondmale advantage with respect to the number of pups sired. When minimal delays were imposed with females in cycling estrus the time of testing within the dark phase did not affect the pattern of sperm competition, but larger litters were born following matings later in the dark phase. When 4 h delays were imposed with the first male mating late in the dark phase a first-male advantage resulted. It is hypothesized that for females in cycling estrus there is a period of peak fertilizability. There is no straight-forward effect of delays between males per se; rather, effects must be analyzed in relation to the period of peak fertilizability. The timing of insemination appears less critical for postpartum females.

Form and development of predation on crickets in adults of Peromyscus maniculatus bairdi and P. leucopus noveboracensis..

Three experiments compared the similarities and differences in attacks on crickets by two species of laboratory-raised cricetid mice, Peromyscus maniculatus bairdi and P. leucopus noveboracensis. In Experiment 1 moderately prey-experienced 1.5-year-old mice of both species concentrated attacks on the crickets' dorsal head. P. leucopus also produced considerable damage to the thorax and showed a greater effect of sessions on the location and latency of attack. In Experiment 2 prey-naive .4- to .8-year-old mice of both species initially damaged crickets randomly and were slow to attack, but after two sessions both species attacked rapidly and displayed the same focus on the dorsal head shown in Experiment 1. However, P. leucopus did not display the thoracic focus shown by this species in Experiment 1. In Experiment 3 the P. leucopus from Experiment 2 were retested at 1.5 years of age without further predatory experience and showed the thoracic focus of attack found in Experiment 1. Young adults of both species markedly and similarly increased the speed and focus of predatory attacks on crickets after limited experience. The attack characteristics of older P. maniculatus differed very little from those of experienced young adults, whereas the attack characteristics of P. leucopus changed as a function of both age and subsequent test experience.

Form and development of predation on crickets in adults of Peromyscus maniculatus bairdi and P. leucopus noveboracensis.

Form and development of predation on crickets in adults of Peromyscus maniculatus bairdi and P. leucopus noveboracensis.

Neurons in the suprachiasmatic area are labelled after intravenous injections of horseradish peroxidase.

Intravenous injections of horseradish peroxidase (HRP) produced labelled neurons in the suprachiasmatic area of house mice (Mus musculus), deer mice (Peromyscus maniculatus bairdi), and white-footed mice (Peromyscus leucopus). In the two species of Peromyscus, a significant proportion of the labelled cells was found within the suprachiasmatic nucleus (SCN). These results suggest that when HRP is injected in the eyes to trace retinal inputs to the hypothalamus, some of the reaction product seen in the SCN may represent blood-borne transport of the enzyme.

Comparative anatomy of the retino-hypothalamic tract in photoperiodic and non-photoperiodic rodents

This study examined whether the nearly symmetrical input from each eye to each suprachiasmatic nucleus previously reported in Syrian hamsters ( Mesocricetus auratus) is a universal feature of retino-hypothalamic projections in photoperiodic rodents. Intraocular injections of horseradish peroxidase (HRP) were used to trace the retino-hypothalamic tract in three species of photoperiodic rodents, Turkish hamster ( Mesocricetus brandti), deer mouse ( Peromyscus maniculatus bairdi) and white-footed mouse ( Peromyscus leucopus) and in the non-photoperiodic house mouse ( Mus musculus). The Turkish hamster displayed a pattern of retinal input to the suprachiasmatic nuclei (SCN) similar to that previously seen in the Syrian hamster. On the other hand, the two photoperiodic species of Peromyscus used in the study showed an asymmetrical distribution of retinal fibers with the heaviest input to each suprachiasmatic nucleus originating from the contralateral eye. This asymmetrical pattern was also evident in house mice and is similar to that previously seen in rats. Therefore, symmetrical retinal input to the SCN is not consistently related to photoperiodism in rodents.

Tests of preferences of deer mice (Peromyscus maniculatus bairdi) for individuals and their odors as a function of sex and estrous condition.

Tests of preferences of deer mice (Peromyscus maniculatus bairdi) for individuals and their odors as a function of sex and estrous condition.

Tests of preferences of deer mice (Peromyscus maniculatus bairdi) for individuals and their odors as a function of sex and estrous condition.

Tests of preferences of deer mice (Peromyscus maniculatus bairdi) for individuals and their odors as a function of sex and estrous condition.

Interactions between males and their sperm during multi-male copulatory episodes of deer mice ( Peromyscus maniculatus)

Twenty triads of one female and two male deer mice, Peromyscus maniculatus bairdi, copulated in tests in which the dynamics of male-male interactions and sperm competition could be analysed. Paternity of offspring was determined with starch-gel electrophoresis. Basic parameters of male copulatory behaviour resembled those of one-male, one-female episodes. Male-male influences on copulatoon were subtle and complex, with a given male somewhat less likely to copulate during the other's copulatory than refractory periods. Males ejaculating first or last gained no reproductive advantage. The male attaining more ejaculations sired more, but not significantly more, offspring than the other male. However, the predictability of litter composition was improved and significant when ejaculations followed by a female post-ejaculatory quiescent period of 1 min or less were discounted. This suggests that male deer mice can essentially cancel the ejaculation of another male by copulating within 1 min of his ejaculation.

Effects of laryngeal denervation on ultrasound production and male sexual behavior in rodents

Adult male house mice (Mus musculus) and deer mice (Peromyscus maniculatus bairdi) were used to investigate the effects of partial denervation of the larynx on ultrasound production. In addition the masculine sexual behavior of vocalizing and muted males was assessed on tests with receptive females. For both species, unilateral transections of the inferior laryngeal nerve (ILN) significantly reduced the proportion of males that emitted ultrasonic vocalizations. However, the inability to vocalize did not prevent the display of male sexual behavior. Bilateral transections of the superior laryngeal nerve (SLN) failed to abolish ultrasound production in males of both species. These nerve transections, however, reduced the amount of ultrasound recorded during postsurgical tests, and in the case of deer mice, cuts of the SLN increased the latency to the first vocalization. The present results confirm the importance of the ILN in the neural control of ultrasonic vocalizations and indicate that, at least in laboratory tests, the ability to emit ultrasounds is not a necessary condition for the display of mating behavior in male rodents.

Hypothyroidism in reproductively inhibited prairie deer mice (Peromyscus maniculatus bairdi) from laboratory populations.

Several thyroid function parameters were compared between reproductively inhibited prairie deer mice of both sexes taken from laboratory populations and corresponding reproductively capable controls. The results of these experiments indicated the following: 1) prairie deer mice females had a statistically significant daily variation in mean serum thyroxine concentration and males displayed a similar trend; 2) total serum thyroxine and triiodothyronine were significantly lower in both male and female reproductively inhibited population animals compared with reproductively capable controls; 3) several morphometric characteristics of the thyroid of male and female population prairie deer mice were significantly different from that of control males and females, suggesting functional hypothyroidism in both sexes; 4) thyroid histology of male population deer mice was different from that of female population animals. In males, the data suggested that thyroid-stimulating hormone (TSH) stimulation was deficient due to some undetermined secondary hypothyroidism. In females, reduced serum thyroxine and triiodothyronine concentrations were observed due to primary hypothyroidism of unknown origin. The interrelationship between thyroid and adrenal function is discussed here and it is concluded that each of the systems may contribute to the observed reproductive inhibition. In particular, it was noted that the mechanism of response between population males and females may be quite different. No conclusive data are available to suggest whether one or the other system is the primary controller of the reproductive inhibition.

Serum ACTH and adrenal histology in reproductively inhibited male prairie deermice ( Peromyscus maniculatus bairdi)

1. 1. Exogenous ACTH will cause adrenal hypertrophy and gonad dysfunction in reproductively capable male deermice. 2. 2. The ultrastructure of the zona fasciculata of inhibited animals is substantially different from ACTH stimulated animals which suggests that ACTH alone does not produce the inhibition. 3. 3. Although ACTH concentrations were variable, there was no clear demonstration that any differences existed between reproductively capable vs inhibited animals at the time when corticosterone is known to be elevated in the inhibited animals. 4. 4. A contributory role for ACTH in promoting inhibition is not ruled out, but neither is it likely that elevated ACTH alone accounts for the observed reproductive inhibition in animals taken from populations.

Seasonal dispersal in a seminatural population of Peromyscus maniculatus

Social factors contributing to seasonal patterns of dispersal in Peromyscus maniculatus bairdi were tentatively identified by partial control of the initial demography, nutrition, predation, and competition. Populations consisting of eight mated pairs of adult mice were established in an open field artificially provided with favorable microhabitats during two springs, one summer, and two falls. The microhabitats were 32 aluminum cylinders 2 m in diameter arranged in 16 couplets on a square grid covering 1.4 ha. Each cylinder enclosed an area of 3.1 m2 containing nest boxes, food, water, and a single small exit to the surrounding fields. Nests were checked every 3rd day for marked individuals over a period of 10 weeks, after which the existing population was removed and a new one established. More individuals were lost from the population during spring and summer than in the fall. Local movements on the study area were not related to the disappearance of mice. Significantly more mothers moved nests between litters than remained. Family groups were most cohesive in fall and were rarely joined by nonrelatives. There was no evidence of agonistic behavior within families. Most mice left the population in the spring and summer when the juveniles were sexually maturing, in contrast to the fall when only the resident adults continued to breed. A sexual search hypothesis proposes that the rate of dispersal increases directly with the rate of recruitment of sexually maturing individuals.

Juvenile ataxia--a new behavioral mutation in the deermouse.

An autosomal recessive behavioral mutation designated juvenile ataxia (ja) was first isolated from F2 progeny of four blonde (bl) Peromyscus maniculatus bairdi siblings. Juvenile ataxic homozygotes exhibit an ataxic gait without an associated tremor from 15 days postpartum. This ataxia continues but does not increase noticeably in severity until between 35 and 43 days of age. Thereafter, a rapid and dramatic improvement in the behavior pattern is seen, so that juvenile ataxic deermice over 45 days of age are phenotypically indistinguishable from wild type or heterozygotes of the same age. Female juvenile ataxic homozygotes rarely breed, while male homozygotes are fully fertile. Linkage tests between juvenile ataxia and blonde suggest that these two mutations are not allelic and are not tightly linked. Testing between juvenile ataxia and a previously described neurological mutant, boggler (bg), indicates that complementation between these two mutations is incomplete, and suggests that boggler and juvenile ataxic may represent allelic mutations.