A lymphosarcoma in an Atlantic salmon (Salmo salar)

A lymphosarcoma that appeared to be of thymic origin and of lymphoblastic type was found in a 3.5-yr-old Atlantic salmon (Salmo salar). The fish was from a population of 60 broodfish maintained at a research fish laboratory. A large tumor mass was found under the left operculum. Small tumor nodules were found on the swim bladder and in the abdominal adipose tissue. The location of this neoplasm differed from those of previously described tumors in this fish species.     

Body and organ mass in agouti and non-agouti deer mice (Peromyscus maniculatus).

Body, adrenal, brain, heart, liver, kidney, spleen and testis masses were determined for agouti and non-agouti deer mice (Peromyscus maniculatus gracilis) of both sexes. Body mass was highest for non-agouti females and lowest for agouti females; and sex differences in body mass were significant for agouti, but not non-agouti, deer mice. Adrenal, brain and liver masses were similar between color morphs; heart mass was greater in agouti males; and kidney, spleen and testis masses were all significantly greater for non-agouti deer mice. Splenomegaly in non-agouti deer mice was prominent, as spleens of non-agouti deer mice were 50% larger than those of agouti animals. Sex differences varied across organs and color morphs. For both color morphs, males had heavier adrenals and brains, whereas females had heavier livers and spleens. Kidney and heart mass was greater for female non-agouti deer mice, but for agouti animals, heart mass was greater in males and kidney mass differed little between the sexes. For both color morphs, testes and spleen mass was altered by photoperiod in 72 deer mice housed under short- or long-day conditions and the effect was stronger in non-agouti animals. This is the first report of splenomegaly and sex-specific body mass differences associated with the non-agouti allele.     

Suspension cultures of human malignant lymphoma in the leukocyte migration test

The effects of supernatants of primary and secondary malignant human lymphoma cell cultures were analyzed as parameters of spontaneous secretion of factors by these cells using the leukocyte migration test (LMT). Spontaneous cultivation for up to five weeks was successful in four cases. The postulated production of mediators, i.e. the inhibitory and stimulating effects on leukocyte migration were characterized by testing the influence of (a) concentration, (b) temperature and (c) absorption with normal blood leukocytes on the effect. Reproducible stimulatory and inhibitory effects on the migration of normal leukocytes were dependent on concentration and temperature and were apparently mediated by one or more factors. The supernatants of a lymphoblastic lymphosarcoma of the T-cell type and of a lymphoblastic lymphosarcoma clearly revealed congruous and reproducible inhibitory effects. A further case of lymphoblastic lymphosarcoma that could not exactly be defined with immunological methods either and a case of centroblastic/centrocytic lymphosarcoma exhibited stimulating effects which could be reduced in a time-dependent manner through preincubation with blood leukocytes. The results of these studies support the assumption that malignant lymphoma cells are capable not only of secreting immunoglobulin, but also of other biologically effective secretion. The effects of such secretion are differentiated into stimulating and inhibitory ones. They might be important for the spreading of a tumor or for resistance of the organism to the disease.     

Febrile response and decrease in circulating lymphocytes following acute infection of white-tailed deer fawns with either a BVDV1 or a BVDV2 strain

Although commonly associated with infection in cattle, bovine viral diarrhea viruses (BVDV) also replicate in many domestic and wildlife species, including cervids. Bovine viral diarrhea viruses have been isolated from a number of cervids, including mule deer (Odocoileus hemionus), European roe deer (Capreolus capreolus), red deer (Cervus elaphus), white-tailed deer (Odocoileus virginianus), and mouse deer (Tragulus javanicus), but little information is available regarding clinical presentation and progression of infection in these species. In preliminary studies of experimental infection of deer with BVDV, researchers noted seroconversion but no clinical signs. In this study, we infected white-tailed deer fawns that were negative for BVDV and for antibodies against BVDV, with either a type 1 or a type 2 BVDV that had been isolated from white-tailed deer. Fawns were monitored for changes in basal temperature, circulating lymphocytes, and platelets. The clinical progression following inoculation in these fawns was similar to that seen with BVDV infections in cattle and included fever and depletion of circulating lymphocytes. Because free-ranging cervid populations are frequently in contact with domestic cattle in the United States, possible transfer of BVDV between cattle and cervids has significant implications for proposed BVDV control programs.     

Exotic deer in southern Latin America: what do we know about impacts on native deer and on ecosystems?

A recent review on exotic cervids concluded that deer introduced to Patagonia impacted habitat and native huemul deer Hippocamelus bisulcus. I evaluate these assertions and amend information about this South American case study. Categorizing deer along narrow characteristics may be too restrictive to allow accurate predictions about interactions. More effective is considering the magnitude of plasticity (behavioral, phenotypic, genetic). The dichotomy of native versus exotic deer masks situations where prevailing ecological conditions are far from ‘native’, such as absence of predators, and such results from artificial settings have limitations. Studies used to contrast effects on vegetation from exotic red deer (Cervus elaphus) versus native huemul did not analyze native deer and provided no data to support conclusions in the review. Huemul were concluded to have high trophic overlap with red deer whose diet, however, was determined in another habitat where the food item of supposed major overlap was absent, and suggesting that red deer might cause exploitation competition was not supported by cited data. There was no mention that huemul are foremost exposed to livestock rather than exotic deer. Concluding that exotic prey including red deer increase predator density resulting in increased predation of huemul (apparent competition), was not supported by cited studies. To the contrary, high-density puma (Puma concolor) could not prevent guanaco (Lama guanicoe) from increasing >13-fold, nor that huemul expanded into these sites. Not only were those studies opposite to conclusions in the review, but none had studied huemul nor predator population trends. Data from little known species like huemul should be used with reservations when aiming at generalizations.     

Allosensitization induced suppression of various murine tumors: role of non-H-2 antigens in antitumor immunity

Presence of alloantigens on various murine tumors was tested by tumor rejection in allosensitized Swiss mice. The results indicated the presence of alloantigen on immunogenic tumors like chemically induced fibrosarcoma (FS), ascitic sarcoma 180 (S 180) and immunogenic variant of lymphosarcoma (LS-A) in Swiss mice, while these antigens could not be detected by this procedure on spontaneous lymphosarcoma (LS). Allosensitization with skin graft was found to offer quantitatively higher antitumor resistance than the allosensitization achieved by allogeneic lymphocytes. Antitumor effect was not seen when tumor cells were inoculated earlier than day 3 of grafting. Further, host immunosuppression with whole body irradiation up to day of 3 of skin grafting abrogated the antitumor effect. H-2 compatible and non-H-2 incompatible skin graft sensitization of host could offer resistance against both S 180 and LS-A. Further, tumor immune mice rejected H-2 compatible, non-H-2 incompatible skin graft significantly earlier.     

Hypocomplementemia associated with naturally occurring lymphosarcoma in pet cats.

Eighty cats were classified by indirect immunofluorescence and histologic diagnosis into four categories: normal, feline leukemia virus (FeLV) infected; normal noninfected; lymphosarcoma-FeLV infected; lymphosarcoma, no FeLV present. All viremic cats with lymphosarcoma were found to be hypocomplementemic and activation of the complement system had occurred via the classical pathway. Sera of cats with lymphosarcoma in the absence of FeLV had varying levels of total hemolytic complement (TCH50) ranging from normal to hypocomplementemic. Approximately 50% of the cats that were viremic but histologically and clinically free of disease had TCH50 levels within normal range, and the remainder exhibited varying degrees of hypocomplementemia.     

Population responses of roe deer to the recolonization of the French Vercors by wolves

In a context of changing carnivore populations worldwide, it is crucial to understand the consequences of these changes for prey populations. The recolonization by wolves of the French Vercors mountain range and the long-term monitoring (2001–2017) of roe deer in this area provided a unique opportunity to assess the effects of wolves on this prey. Roe deer was the main prey of wolves in the west Vercors mountain range during this recolonization. We compared roe deer abundance and fawn body mass in two contrasted areas of a wolf pack territory: a central area (core of the territory characterized by an intense use by wolves) and a peripheral area (used more occasionally). Roe deer population growth rates were lower in the central area between 2001 and 2006, resulting in a decline in roe deer abundance. Roe deer abundance substantially dropped in the two study areas after an extremely severe winter but the abundance of roe deer in the central area facing with wolves was slower to recover and remained at lower abundance levels for 6 years. Fawn body mass was consistently lower in the central area, varied similarly as roe deer abundance, and was not influenced by weather conditions or red deer population abundance. Altogether, the effects of wolves on roe deer in the central area occurred during a 10-year period following the establishment of wolves, through the interplay between wolf predation (before wolves started preying on red deer), harsh winter conditions and possibly naivety of prey to this recolonizing predator.     

Seasonal flooding effects on deer in the Mississippi river batture

Effective deer management requires managers to distinguish between the density-dependent influence of harvest and local environmental factors. The Batture region of the Lower Mississippi River Valley comprises land adjacent to the river that is not protected by the levee system, and is therefore subject to seasonal flooding with potential to influence the morphology and demographics of white-tailed deer (Odocoileus virginianus). Using harvest records of 42,954 females and 3,588 males from 61 Batture properties in Mississippi and Louisiana, we created linear regression models of deer body development and recruitment indices to compare the influence of seasonal flooding, harvest rate, growing season weather, and agronomic forage availability during 1988–2016. Overall, deer in the Batture appeared to be more influenced by extrinsic factors than by harvest. Seasonal flooding appeared in every model and generally had stronger effects than weather or harvest variables. Flooding from 1 to 2 years prior, regardless of season, was correlated with greater female body mass, lactation rates, and antler mass of trophy males, possibly reflecting silt deposition effects on soil fertility and promotion of new understory forages. Conversely, current-year flooding effects were invariably negative, implying direct effects of displacement. Summer flooding was concentrated during late gestation and peak parturition periods, and exhibited the potential to reduce fall lactation rates by 18%. Harvest rates correlated negatively with female body mass and had no correlation with lactation or antler mass. We detected contrasting long-term trends of decreasing body mass and increasing harvest rate that may reflect deteriorating habitat. Similar to flooding, increased temperatures and rainfall had negative effects for the current year, whereas increased temperatures had positive effects when occurring in the previous year. Surprisingly, annual variation in the amount of soybeans planted appeared in one model only, exhibiting a small positive effect on antler mass. We hypothesize that extensive planting of soybeans in levee-protected lands just outside the Batture maintained substantial soybean availability despite variation in the amount planted. Given the dominating influence of flooding and weather on deer physical and reproductive parameters in the Batture, these extrinsic variables should be incorporated into the interpretation of harvest data. The common practice of curtailing harvest, particularly female harvest, following years with extensive flooding is likely counterproductive unless intensive flooding occurs during summer. © 2019 The Wildlife Society.     

Failure of white-tailed deer, Odocoileus virginianus L., to sustain a population of cattle ticks, Boophilus annulatus (Say), through successive generations

Cattle ticks, Boophilus annulatus (Say), previously reared only on cattle, were placed on 3 white-tailed deer, Odocoileus virginianus L. Ticks were maintained through successive generations solely on the same deer as they aged (3, 6, and 9 mo of age) and received repeated challenges (0, 1, and 2 previous challenges). Cattle were infested simultaneously to assess tick viability and provide a comparison of tick numbers, female weight, egg mass weight, and egg hatch. The initial infestation (3,000 larvae/animal) produced a mean of 12.7 and 506.7 females from deer and cattle, respectively. Ticks recovered from deer weighed less, laid smaller egg masses, and had lower egg hatchability than cattle-reared ticks. A second infestation (3,000 larvae/animal) produced a 6.3-fold reduction in tick numbers on deer (means = 2.0 females/deer), whereas the number on cattle increased (means = 578.0 females/calf). Ticks reared on the deer were again smaller, laid fewer eggs, and had lower egg hatch, although differences were not significant. A third infestation of deer (1,900 larvae/deer) produced only 1 engorged female tick and no viable eggs, thus eliminating the population of deer-reared ticks within 3 generations. Results of the study suggest that a population of B. annulatus will not be sustained indefinitely through time solely on deer; thus, efforts to reduce deer populations severely as a means of eradicating ticks are unnecessary.     

The effect of hydrocortisone treatment on the in vivo phosphorylation of a subgroup of non-histone nuclear proteins in the mouse lymphosarcoma P1798

The $\text{in vivo}$ phosphorylation of a small subgroup of non-histone nuclear proteins, similar to the high mobility group (HMG) proteins described by Goodwin and Johns ($\text{Methods in Cell Biology}$ (1977) Vol. XVI, eds. G. Stein, J. Stein and L.J. Kleinsmith, pp. 257–267, Academic Press, New York), was studied in the P1798 mouse lymphosarcoma. A single injection of cortisol, resulting in a 50% reduction in tumor mass of the sensitive strain of this tumor, caused a marked suppression in phosphorylation of at least three of these proteins, independent of any apparent change in protein concentration. No such change was observed in the cortisol-resistant strain, and it is suggested that the effect of cortisol in causing regression of this tumor might be mediated via changes in phosphorylation of specific nuclear proteins.     

Targeted disruption of CD44 in MDAY-D2 lymphosarcoma cells has no effect on subcutaneous growth or metastatic capacity

CD44 splice variants have been shown to be involved in metastasis of carcinomas. In addition, the standard form of CD44 has been implicated in metastasis, particularly of melanomas and lymphomas. To investigate this, we have generated a CD44-negative mutant of the highly metastatic murine MDAY-D2 lymphosarcoma. The two CD44 alleles of this diploid cell line were sequentially disrupted by homologous recombination, using isogenic CD44 genomic constructs interrupted by a neomycin or hygromycin resistance-conferring gene. The resulting double knockout (DKO) cells had completely lost the capacity to bind to immobilized hyaluronic acid, but did not differ from MDAY-D2 cells in integrin expression or in vitro growth. Subcutaneous (s.c.) growth potential and metastatic capacity of MDAY-D2 and DKO cells were assessed by s.c. and i.v. injection of the lowest cell dose (10(3) or 10(4), respectively) that gave rise to tumor formation by MDAY-D2 cells in approximately 100% of the mice. Quite unexpectedly, we observed no difference at all in either s.c. growth rate or local invasion into surrounding tissues between MDAY-D2 cells and the CD44-negative DKO cells. Also hematogenous metastasis formation upon i.v. injection was similar: both parental and DKO cells metastasized extensively to the spleen, liver, and bone marrow. We conclude that, at least for these MDAY-D2 lymphosarcoma cells, the standard form of CD44 is dispensable for tumor growth and metastasis. Our results show that targeted disruption of genes in tumor cells is a feasible approach to study their role in tumorigenesis and metastasis.     

带岭林区马鹿冬季食性研究

1985-1987年在黑龙江省带岭林区,使用粪便显微组织学分析技术井结合野外啃食调查,对马魔冬季食性进行了研究。结果表明,杨,桦,柳,紫椴是其主要的冬季食物(46.9% ,19.1% , 9.7%、 8.3% )。马鹿对杨、柳、青楷槭有正选择性,对桦、紫椴、刺老芽、接骨木有负选择性．马鹿对它们选择性的强弱顺序为：青槽槭>柳>杨>接骨木>刺者芽>紫椴>桦。被啃食植物中半纤维素的含量和马鹿对它们的选择性之间存在着一定的负相关关系。冬季马鹿并不缺乏蛋白质,而能量对越冬的马鹿可能是一个较为关键的因子。     

Forestomach pH in hunted roe deer (Capreolus capreolus) in relation to forestomach region, time of measurement and supplemental feeding and comparison among wild ruminant species

There is a debate whether supplemental feeding of deer bears the risk of inducing health problems, in particular acidosis. Here, the pH values of forestomach contents of free-ranging roe deer (Capreolus capreolus) shot in areas with and without supplemental winter feeding were compared. pH was similar in the dorsal and ventral rumen, but lower at these sites than in the Atrium ruminis, where it was again lower than in the reticulum; this pattern corresponds to expectations based on differences in the presence of saliva at the different sites of the forestomach. pH was lower with increasing time that elapsed between death of the animal and measuring pH in unsupplemented animals and was lower in unsupplemented animals in May/June than later in the year. Animals with supplemental winter feeding had significantly lower rumen pH (5.5) than animals without food supplementation (5.7). These data suggest that supplemental feeding of roe deer has the potential to lower forestomach pH. Although pH values measured in supplemented animals in this study would be considered indicative of rumen acidosis in domestic cattle, they are within the range previously measured in various free-ranging Odocoilid species, including roe deer; were of a similar magnitude as the May/June values of unsupplemented roe deer in this study; and must be considered with respect to potentially rapid declines in pH between death of the animal and pH measurement. Given methodological problems, analyses of literature data from free-ranging wild ruminants provide little evidence for a systematic variation of rumen pH with feeding type and body mass, but lead to the hypothesis that some New World cervids, including the roe deer, might either naturally have lower pH values than other ruminants or rumen contents whose pH drops rapidly after death.     

Linking White-Tailed Deer Density,Nutrition, and Vegetation in a Stochastic Environment

Density-dependent behavior underpins white-tailed deer (Odocoileus virginianus) theory and management application in North America, but strength or frequency of the phenomenon has varied across the geographic range of the species. The modifying effect of stochastic environments and poor-quality habitats on density-dependent behavior has been recognized for ungulate populations around the world, including white-tailed deer populations in South Texas, USA. Despite the importance of understanding mechanisms influencing density dependence, researchers have concentrated on demographic and morphological implications of deer density. Researchers have not focused on linking vegetation dynamics, nutrition, and deer dynamics. We conducted a series of designed experiments during 2004–2012 to determine how strongly white-tailed deer density, vegetation composition, and deer nutrition (natural and supplemented) are linked in a semi-arid environment where the coefficient of variation of annual precipitation exceeds 30%. We replicated our study on 2 sites with thornshrub vegetation in Dimmit County, Texas. During late 2003, we constructed 6 81-ha enclosures surrounded by 2.4-m-tall woven wire fence on each study site. The experimental design included 2 nutrition treatments and 3 deer densities in a factorial array, with study sites as blocks. Abundance targets for low, medium, and high deer densities in enclosures were 10 deer (equivalent to 13 deer/km²), 25 deer (31 deer/km²), and 40 deer (50 deer/km²), respectively. Each study site had 2 enclosures with each deer density. We provided deer in 1 enclosure at each density with a high-quality pelleted supplement ad libitum, which we termed enhanced nutrition; deer in the other enclosure at each density had access to natural nutrition from the vegetation. We conducted camera surveys of deer in each enclosure twice per year and added or removed deer as needed to approximate the target densities. We maintained >50% of deer ear-tagged for individual recognition. We maintained adult sex ratios of 1:1–1:1.5 (males:females) and a mix of young and older deer in enclosures. We used reconstruction, validated by comparison to known number of adult males, to make annual estimates of density for each enclosure in analysis of treatment effects. We explored the effect of deer density on diet composition, diet quality, and intake rate of tractable female deer released into low- and high-density enclosures with natural nutrition on both study sites (4 total enclosures) between June 2009 and May 2011, 5 years after we established density treatments in enclosures. We used the bite count technique and followed 2–3 tractable deer/enclosure during foraging bouts across 4 seasons. Proportion of shrubs, forbs, mast, cacti, and subshrubs in deer diets did not differ (P > 0.57) between deer density treatments. Percent grass in deer diets was higher (P = 0.05) at high deer density but composed only 1.3 ± 0.3% (SE) of the diet. Digestible protein and metabolizable energy of diets were similar (P > 0.45) between deer density treatments. Likewise, bite rate, bite size, and dry matter intake did not vary (P > 0.45) with deer density. Unlike deer density, drought had dramatic (P ≤ 0.10) effects on foraging of tractable deer. During drought conditions, the proportion of shrubs and flowers increased in deer diets, whereas forbs declined. Digestible protein was 31%, 53%, and 54% greater (P = 0.06) during non-drought than drought during autumn, winter, and spring, respectively. We studied the effects of enhanced nutrition on the composition and quality of tractable female deer diets between April 2007 and February 2009, 3 years after we established density treatments in enclosures. We also estimated the proportion of supplemental feed in deer diets. We used the 2 low-density enclosures on each study site, 1 with enhanced nutrition and 1 with natural nutrition (4 total enclosures). We again used the bite count technique and 2–3 tractable deer living in each enclosure. We estimated proportion of pelleted feed in diets of tractable deer and non-tractable deer using ratios of stable isotopes of carbon. Averaged across seasons and nutrition treatments, shrubs composed a majority of the vegetation portion of deer diets (44%), followed by mast (26%) and forbs (15%). Enhanced nutrition influenced the proportion of mast, cacti, and flowers in the diet, but the nature and magnitude of the effect varied by season and year. The trend was for deer in natural-nutrition enclosures to eat more mast. We did not detect a statistical difference (P = 0.15) in the proportion of shrubs in diets between natural and enhanced nutrition, but deer with enhanced nutrition consumed 7–24% more shrubs in 5 of 8 seasons. Deer in enhanced-nutrition enclosures had greater (P = 0.03) digestible protein in their overall diet than deer in natural-nutrition enclosures. The effect of enhanced nutrition on metabolizable energy in overall diets varied by season and was greater (P < 0.04) for enhanced-nutrition deer during summer and autumn 2007 and winter 2008. In the enhanced-nutrition treatment, supplemental feed averaged 47–80% of the diet of tractable deer. Of non-tractable deer in all density treatments with enhanced nutrition, 97% (n = 128 deer) ate supplemental feed. For non-tractable deer averaged across density treatments, study sites, and years, percent supplemental feed in deer diets exceeded 70% for all sex and age groups. We determined if increasing deer density and enhanced nutrition resulted in a decline in preferred forbs and shrubs and an increase in plants less preferred by deer. We sampled all 12 enclosures via 20, 50-m permanent transects in each enclosure. Percent canopy cover of preferred forbs was similar (P = 0.13) among deer densities averaged across nutrition treatments and sampling years (low density: = 8%, SE range 6–10; medium density: 5%, 4–6; high density: 4%, 3–5; SE ranges are presented because SEs associated with backtransformed means are asymetrical). Averaged across deer densities, preferred forb canopy cover was similar between nutrition treatments in 2004; but by 2012 averaged 20 ± 17–23% in enhanced-nutrition enclosures compared to 10 ± 8–13% in natural-nutrition enclosures (P = 0.107). Percent canopy cover of other forbs, preferred shrubs, other shrubs, and grasses, as well as Shannon's index, evenness, and species richness were similar (P > 0.10) among deer densities, averaged across nutrition treatments and sampling years. We analyzed fawn:adult female ratios, growth rates of fawns and yearlings, and survival from 6 to 14 months of age and for adults >14 months of age. We assessed adult body mass and population growth rates (lambda apparent, λ_APP) to determine density and nutrition effects on deer populations in the research enclosures during 2004–2012. Fawn:adult female ratios declined (P = 0.04) from low-medium density to high density in natural-nutrition enclosures but were not affected (P = 0.48) by density in enhanced nutrition enclosures although, compared to natural nutrition, enhanced nutrition increased fawn:adult female ratios by 0.15 ± 0.12 fawns:adult female at low-medium density and 0.44 ± 0.17 fawns:adult female at high density. Growth rate of fawns was not affected by deer density under natural or enhanced nutrition (P > 0.17) but increased 0.03 ± 0.01 kg/day in enhanced-nutrition enclosures compared to natural nutrition (P < 0.01). Growth rate of yearlings was unaffected (P > 0.71) by deer density, but growth rate increased for males in some years at some density levels in enhanced-nutrition enclosures. Adult body mass declined in response to increasing deer density in natural-nutrition enclosures for both adult males (P < 0.01) and females (P = 0.10). Enhanced nutrition increased male body mass, but female mass did not increase compared to natural nutrition. Survival of adult males was unaffected by deer density in natural- (P = 0.59) or enhanced- (P = 0.94) nutrition enclosures. Survival of adult females was greatest in medium-density enclosures with natural nutrition but similar at low and high density (P = 0.04). Enhanced nutrition increased survival of females (P < 0.01) and marginally for males (P = 0.11). Survival of fawns 6–14 months old was unaffected (P > 0.35) by density in either natural- or enhanced-nutrition treatments but was greater (P = 0.04) under enhanced nutrition. Population growth rate declined (P = 0.06) with increasing density in natural-nutrition enclosures but not (P = 0.55) in enhanced nutrition. Enhanced nutrition increased λ_APP by 0.32. Under natural nutrition, we found only minor effects of deer density treatments on deer diet composition, nutritional intake, and plant communities. However, we found density-dependent effects on fawn:adult female ratios, adult body mass, and population growth rate. In a follow-up study, deer home ranges in our research enclosures declined with increasing deer density. We hypothesized that habitat quality varied among home ranges and contributed to density-dependent responses. Variable precipitation had a greater influence on deer diets, vegetation composition, and population parameters than did deer density. Also, resistance to herbivory and low forage quality of the thornshrub vegetation of our study sites likely constrained density-dependent behavior by deer. We posit that it is unlikely that, at our high-density (50 deer/km²) and perhaps even medium-density (31 deer/km²) levels, negative density dependence would occur without several wet years in close association. In the past century, this phenomenon has only happened once (1970s). Thus, density dependence would likely be difficult to detect in most years under natural nutrition in this region. Foraging by deer with enhanced nutrition did not result in a reduction in preferred plants in the vegetation community and had a protective effect on preferred forbs because ≤53% of deer diets consisted of vegetation. However, enhanced nutrition improved fitness of individual deer and deer populations, clearly demonstrating that nutrition is limiting for deer populations under natural conditions in western South Texas. © 2019 The Authors. Wildlife Monographs published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

White-tailed deer as hosts of cattle fever-ticks

A penned study for obtaining definitive information on the status of white-tailed deer (Odocoileus virginianus) as a host for cattle feverticks (Boophilus microplus) was conducted on St. Croix of the U.S. Virgin Islands. Four generations of fever-ticks were propagated on one deer during a six month period. Nine wild white-tailed deer also were collected from four insular estates to evaluate the carrier status of these animals on an island where cattle fever-ticks are indigenous. Two deer were infested with B. microplus where contact with domestic livestock had not occurred for 20 years; five deer were free of B. microplus where a vigorous cattle dipping program had been practiced for three years; and, two deer were infested with B. microplus where contact with fever-tick infested cattle occurred at irregular intervals. It was concluded that white-tailed deer constitute a host species for B. microplus and must be considered in future fever tick eradication endeavors. This study also suggested that, through routine dipping of cattle, fever ticks may be eradicated from an area where cattle and deer cohabit the same premises.     

Functional dietary response of Asian black bears to changes in sika deer density

Omnivores are generally opportunistic foragers and have a flexible dietary response to resource abundance and availability. Their populations may consist of individuals that differ from each other in terms of their trophic positions, which implies that the dietary response to resource fluctuations differs within a population. We investigated how changes in the abundance of sika deer (Cervus nippon) affected dietary variation and body condition in the Asian black bear (Ursus thibetanus). We used fecal analysis, nitrogen stable isotopes (δ¹⁵N), and body measurements to determine whether the variation in dietary meat content of Asian black bears is positively related to variations in the density of the sika deer population, whether male bears have a higher trophic position compared to females, and whether dietary meat content is positively related with body mass or body condition of bears. We found a positive correlation between the occurrence of deer remains in bear feces and deer density, suggesting that bears change their diet in response to temporal changes in deer density. Male bears had higher δ¹⁵N values than females, and neither values varied when deer density decreased. Males selectively consumed deer after a reduction in deer density, whereas females consistently consumed more plant-based diet. The δ¹⁵N values were positively related with body mass of adult (>4 yr) bears but had no relationship with body condition of bears of either sex or any age class. Deer seem to be an important food source for large adult males, which have an advantage in mating. Thus, increasing herbivore abundance and availability altered the foraging strategy of Asian black bears, but the importance of herbivore on bear diet differs within a population.