Predicting woodrat (Neotoma) responses to anthropogenic warming from studies of the palaeomidden record

Aim The influence of anthropogenic climate change on organisms is an area of great scientific concern. Increasingly there is recognition that abrupt climate transitions have occurred over the late Quaternary; studies of these shifts may yield insights into likely biotic responses to contemporary warming. Here, we review research undertaken over the past decade investigating the response of Neotoma (woodrats) body size and distribution to climate change over the late Quaternary (the last 40,000 years). By integrating information from woodrat palaeomiddens, historical museum specimens and field studies of modern populations, we identify potential evolutionary responses to climate change occurring over a variety of temporal and spatial scales. Specifically, we characterize climatic thresholds in the past that led to local species extirpation and/or range alterations rather than in situ adaptation, and apply them to anticipate potential biotic responses to anthropogenic climate change. Location Middens were collected at about 55 sites scattered across the western United States, ranging from about 34 to 46° N and about 104 to 116° W, respectively. Data for modern populations were drawn from studies conducted in Death Valley, California, Missoula, Montana and the Sevilleta LTER site in central New Mexico. Methods We analysed faecal pellets from midden series collected at numerous cave sites across the western United States. From these we estimated body mass using techniques validated in earlier studies. We compared body size fluctuations at different elevations in different regions and integrated these results with studies investigating temperature–body size tradeoffs in modern animals. We also quantify the rapidity of the size changes over the late Quaternary to estimate the evolutionary capacity of woodrats to deal with predicted rates of anthropogenic climate change over the next century. Results We find remarkable similarities across the geographical range to late Quaternary climate change. In the middle of the geographical range woodrats respond in accordance to Bergmann's rule: colder climatic conditions select for larger body size and warmer conditions select for smaller body size. Patterns are more complicated at range boundaries, and local environmental conditions influence the observed response. In general, woodrat body size fluctuates with approximately the same amplitude and frequency as climate; there is a significant and positive correlation between woodrat body size and generalized climate proxies (such as ice core records). Woodrats have achieved evolutionary rates of change equal to or greater than those needed to adapt in situ to anthropogenic climate change. Main conclusions In situ body size evolution is a likely outcome of climate change, and such shifts are part of a normal spectrum of adaptation. Woodrats appear to be subject to ongoing body size selection in response to fluctuating environmental conditions. Allometric considerations suggest that these shifts in body size lead to substantial changes in the physiology, life history and ecology of woodrats, and on their direct and indirect interactions with other organisms in the ecosystem. Our work highlights the importance of a finely resolved and long‐term record in understanding biotic responses to climatic shifts.     

Ambient temperature influences diet selection and physiology of an herbivorous mammal, Neotoma albigula

The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of juniper in its diet varies seasonally. We tested whether changes in juniper consumption are due to changes in ambient temperature and what the physiological consequences of consuming plant secondary compounds (PSCs) at different ambient temperatures might be. Woodrats were acclimated to either 20 degrees C or 28 degrees C. Later, they were given two diets to choose from (50% juniper and a nontoxic control) for 7 d. Food intake, resting metabolic rate (RMR), and body temperature (T(b)) were measured over the last 2 d. Woodrats at 28 degrees C ate significantly less juniper, both proportionally and absolutely, than woodrats at 20 degrees C. RMRs were higher for woodrats consuming juniper regardless of ambient temperature, and T(b) was higher for woodrats consuming juniper at 28 degrees C than for woodrats eating control diet at 28 degrees C. Thus, juniper consumption by N. albigula is influenced by ambient temperature. We conclude that juniper may influence thermoregulation in N. albigula in ways that are helpful at low temperatures but harmful at warmer temperatures in that juniper PSCs may be more toxic at warmer temperatures. The results suggest that increases in ambient temperature associated with climate change could significantly influence foraging behavior of mammalian herbivores.     

Pollen-based quantitative reconstructions of Holocene climate variability in NW Romania

A modern analogue technique is applied to two high-resolution pollen sequences from NW Romania to provide the first quantitative evidence for winter, summer and annual temperatures and for precipitation across the Holocene in this region.

The pollen-based climate reconstructions allow the identification of four main intervals: i) an early, less stable period between 11,700 and 11,200 cal. yr BP; (ii) generally stable conditions between 11,200 and 8300 cal. yr BP with winter and annual temperatures and precipitation higher than at present, and summer temperatures about the same; (iii) lower winter and annual temperatures, and higher summer temperatures and precipitation between 8000 and 2400 cal. yr BP; (iv) warmer winter and annual temperatures and lower precipitation for the last 2400 years, whereas summer temperatures became cooler at Steregoiu and remained stable at Preluca Tiganului.

The pollen-based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the Holocene, but the trends appear to be less consistent for summer temperatures.

Our pollen-based reconstructions revealed several short-term climatic oscillations during the Holocene, the strongest of which occur between 10,300–10,100, 8300–8000, 6800–6400, 5100–4900, 4000–3600 and 3200–3000 cal. yr BP.     

Ambient temperature influences tolerance to plant secondary compounds in a mammalian herbivore

Growing evidence suggests that plant secondary compounds (PSCs) ingested by mammals become more toxic at elevated ambient temperatures, a phenomenon known as temperature-dependent toxicity. We investigated temperature-dependent toxicity in the desert woodrat (Neotoma lepida), a herbivorous rodent that naturally encounters PSCs in creosote bush (Larrea tridentata), which is a major component of its diet. First, we determined the maximum dose of creosote resin ingested by woodrats at warm (28–29°C) or cool (21–22°C) temperatures. Second, we controlled the daily dose of creosote resin ingested at warm, cool and room (25°C) temperatures, and measured persistence in feeding trials. At the warm temperature, woodrats ingested significantly less creosote resin; their maximum dose was two-thirds that of animals at the cool temperature. Moreover, woodrats at warm and room temperatures could not persist on the same dose of creosote resin as woodrats at the cool temperature. Our findings demonstrate that warmer temperatures reduce PSC intake and tolerance in herbivorous rodents, highlighting the potentially adverse consequences of temperature-dependent toxicity. These results will advance the field of herbivore ecology and may hone predictions of mammalian responses to climate change.     

Trends in water quality and discharge confound long-term warming effects on river macroinvertebrates

1. Climate‐change effects on rivers and streams might interact with other pressures, such as pollution, but long‐term investigations are scarce. We assessed trends among macroinvertebrates in 50 southern English streams in relation to temperature, discharge and water quality over 18 years (1989–2007). 2. Long‐term records, coupled with estimates from inter‐site calibrations of 3–4 years, showed that mean stream temperatures in the study area had increased by 2.1–2.9 °C in winter and 1.1–1.5 °C in summer over the 26 year period from 1980 to 2006, with trends in winter strongest. 3. While invertebrate assemblages in surface‐fed streams were constant, those in chalk‐streams changed significantly during 1989–2007. Invertebrate trends correlated significantly with temperature, but effects were spurious because (i) assemblages gained taxa typical of faster flow or well‐oxygenated conditions, contrary to expectations from warming; (ii) more invertebrate families increased in abundance than declined and (iii) concomitant changes in water quality (e.g. declining orthophosphate, ammonia and biochemical oxygen demand), or at some sites changes in discharge, explained more variation in invertebrate abundance and composition than did temperature. 4. These patterns were reconfirmed in both group‐ and site‐specific analyses. 5. We conclude that recent winter‐biased warming in southern English chalk‐streams has been insufficient to affect invertebrates negatively over a period of improving water quality. This implies that positive management can minimize some climate‐change impacts on stream ecosystems. Chalk‐stream invertebrates are sensitive, nevertheless, to variations in discharge, and detectable changes could occur if climate change alters flow pattern. 6. Because climatic trends now characterize many inter‐annual time‐series, we caution other investigators to examine whether putative effects on ecological systems are real or linked spuriously to other causes of change.     

The effects of climate change on the phenology of winter birds in Yokohama, Japan

Observations made largely from summer breeding sites in Europe and North America have been used to document the effects of climate change on many bird species. We extend these studies by examining 23 years of observations between 1986 and 2008 of six winter bird species made by citizens at a city park in Yokohama, Japan. Bird species arrive in autumn and spend the winter in the area, before departing in the late winter or spring. On average, birds species are arriving 9 days later than in the past and are departing on average 21 days earlier, meaning that the average duration of their stay in Yokohama is about 1 month shorter now than in the past. Patterns of changes over time varied among species, but departure dates changed for more species than did arrival dates. Dates of departure and arrival were sometimes correlated with monthly average temperatures—later arrivals and earlier departures were associated with warmer temperatures. In addition, interannual variation in arrival and departure dates were strongly correlated across species, suggesting that species were responding to the same or similar environmental cues. This study provides a clear demonstration of the value of using citizens to make observations that contribute to research in climate change biology.     

Body temperature null distributions in reptiles with nonzero heat capacity: seasonal thermoregulation in the American alligator (Alligator mississippiensis)

Regulation of body temperature may increase fitness of animals by ensuring that biochemical and physiological processes proceed at an optimal rate. The validity of current methods of testing whether or not thermoregulation in reptiles occurs is often limited to very small species that have near zero heat capacity. The aim of this study was to develop a method that allows estimation of body temperature null distributions of large reptiles and to investigate seasonal thermoregulation in the American alligator (Alligator mississippiensis). Continuous body temperature records of wild alligators were obtained from implanted dataloggers in winter (n=7, mass range: 1.6-53.6 kg) and summer (n=7, mass range: 1.9-54.5 kg). Body temperature null distributions were calculated by randomising behavioural postures, thereby randomly altering relative animal surface areas exposed to different avenues of heat transfer. Core body temperatures were predicted by calculations of transient heat transfer by conduction and blood flow. Alligator body temperatures follow regular oscillations during the day. Occasionally, body temperature steadied during the day to fall within a relatively narrow range. Rather than indicating shuttling thermoregulation, however, this pattern could be predicted from random movements. Average daily body temperature increases with body mass in winter but not in summer. Daily amplitudes of body temperature decrease with increasing body mass in summer but not in winter. These patterns result from differential exposure to heat transfer mechanisms at different seasons. In summer, alligators are significantly cooler than predictions for a randomly moving animal, and the reverse is the case in winter. Theoretical predictions show, however, that alligators can be warmer in winter if they maximised their sun exposure. We concluded that alligators may not rely exclusively on regulation of body temperature but that they may also acclimatise biochemically to seasonally changing environmental conditions.     

Lateglacial climate development in NW Romania — Comparative results from three quantitative pollen-based methods

This paper provides quantitative reconstructions of the Lateglacial changes in four climate parameters from two fine-resolution pollen profiles in the Gutaiului Mountains, NW Romania. Climate estimates are based on two modern analogue techniques (with and without considering vegetation types) and weighted averaging partial least squares regression (WA-PLS), giving evidence for several climatic fluctuations during the period from > 14,700 to 11,500 cal. yr BP. The comparative results of the two modern analogue techniques show consistent trends of climate changes that are also coherent at both sites, but these results appear to largely disagree compared with climate reconstruction provided by WA-PLS.The modern analogue techniques revealed four intervals with low temperatures: prior to 14,700 cal. yr BP, between 13,950 and 13,800; 13,400 and 13,200; and 12,700 and 11,700 cal. yr BP. The temperature declines were more pronounced for winter than for summer, suggesting an intensification of seasonality, which together with a drop in precipitation indicates an increase in continentality. The Younger Dryas is the most pronounced cooling phase with winter temperatures ~ 14–16 °C colder than modern conditions, annual and summer temperatures ~ 2–5 °C and ~ 2 °C, respectively below present ones. Precipitation was ~ 400–500 mm, half that of present. During the Bølling and Allerød, summer temperatures were close to modern values (13 to 17 °C), whereas winter (− 6 to − 12 °C) and annual temperatures (0.5 to 6 °C) as well as precipitation were (550 to 700 mm) lower, indicating more continental conditions compared to the present-day climate.     

Climate warming is associated with smaller body size and shorter lifespans in moose near their southern range limit

Despite the importance of body size for individual fitness, population dynamics and community dynamics, the influence of climate change on growth and body size is inadequately understood, particularly for long‐lived vertebrates. Although temporal trends in body size have been documented, it remains unclear whether these changes represent the adverse impact of climate change (environmental stress constraining phenotypes) or its mitigation (via phenotypic plasticity or evolution). Concerns have also been raised about whether climate change is indeed the causal agent of these phenotypic shifts, given the length of time‐series analysed and that studies often do not evaluate – and thereby sufficiently rule out – other potential causes. Here, we evaluate evidence for climate‐related changes in adult body size (indexed by skull size) over a 4–decade period for a population of moose (Alces alces) near the southern limit of their range whilst also considering changes in density, predation, and human activities. In particular, we document: (i) a trend of increasing winter temperatures and concurrent decline in skull size (decline of 19% for males and 13% for females) and (ii) evidence of a negative relationship between skull size and winter temperatures during the first year of life. These patterns could be plausibly interpreted as an adaptive phenotypic response to climate warming given that latitudinal/temperature clines are often accepted as evidence of adaptation to local climate. However, we also observed: (iii) that moose with smaller skulls had shorter lifespans, (iv) a reduction in lifespan over the 4‐decade study period, and (v) a negative relationship between lifespan and winter temperatures during the first year of life. Those observations indicate that this phenotypic change is not an adaptive response to climate change. However, this decline in lifespan was not accompanied by an obvious change in population dynamics, suggesting that climate change may affect population dynamics and life‐histories differently.     

Seasonal changes of thermoregulatory efficiency in Djungarian hamsters

In their natural habitat, Djungarian hamsters are faced with dramatic seasonal changes. This requires various morphological and physiological adaptations allowing cope with harsh climate and food shortage, particularly in winter. These seasonal changes are controlled by the photoperiod and can be observed also in the laboratory at room temperature. The aim of the present study was to investigate if the efficiency of thermoregulation also depends on the photoperiod. For this reason, Djungarian hamsters were transferred to short-day conditions (SDC) with 8 h light and 16 h darkness. Two-thirds of the animals were classified as responders showing the typical seasonal changes – decrease of body mass, fur change, testes regression, vagina closing. The total activity per day did not change but, the nocturnal activity was spread over the longer dark time. The body temperature decreased, and the animals showed regular daily torpor. To investigate the thermoregulatory efficiency, body temperatures were correlated with motor activity. The obtained regression coefficients describe formally the effect of motor activity on body temperature, a measure for the efficiency of thermoregulation. In SDC, the coefficients were elevated, both during rest and activity, i.e. the same amount of activity did produce a larger increase in body temperature. Under field conditions, this might be an additional mechanism to compensate the bigger in winter heat loss. Also, the high coefficients may support the increase in body temperature at the end of a torpor phase by a bout of motor activity. The results show that, seasonal changes of thermoregulatory efficiency are an effective accessory way to cope with different temperatures in hamsters’ natural environment.     

Pre-1930 unstable relationship between climate and tree-ring width of Pinus taiwanensis hayata in southeastern China

Although it has been widely recognized that tree-ring response to climate drivers may change over recent decades, often due to anthropogenic environment changes, there are fewer reports of such changes in earlier pre-warming periods. In this paper we report on the pre-1930 unstable relationship between climate and tree-ring width (TRW) of Pinus taiwanensis Hayata in southeastern China based on reliable long-term temperature data. TRW of P. taiwanensis is strongly controlled by temperatures in two seasons, previous spring to summer (March to August, mainly June to July) and previous winter to current spring (December to March). However, TRW are insensitive to previous spring to summer temperature between 1890 and 1930. Reduced summer temperature variability, changing regimes of spring-summer temperature and precipitation, and complicated tree physiological processes behind the complex growth-climate relationship are the more likely causes of this phenomenon. This study adds to the body of knowledge that lower climate sensitivity of tree rings is not specific to the most recent decades.     

Behavioural Responses to Thermal Conditions Affect Seasonal Mass Change in a Heat-Sensitive Northern Ungulate

Background

Empirical tests that link temperature-mediated changes in behaviour (activity and resource selection) to individual fitness or condition are currently lacking for endotherms yet may be critical to understanding the effect of climate change on population dynamics. Moose (Alces alces) are thought to suffer from heat stress in all seasons so provide a good biological model to test whether exposure to non-optimal ambient temperatures influence seasonal changes in body mass. Seasonal mass change is an important fitness correlate of large herbivores and affects reproductive success of female moose.

Methodology/Principal Findings

Using GPS-collared adult female moose from two populations in southern Norway we quantified individual differences in seasonal activity budget and resource selection patterns as a function of seasonal temperatures thought to induce heat stress in moose. Individual body mass was recorded in early and late winter, and autumn to calculate seasonal mass changes (n = 52 over winter, n = 47 over summer). We found large individual differences in temperature-dependent resource selection patterns as well as within and between season variability in thermoregulatory strategies. As expected, individuals using an optimal strategy, selecting young successional forest (foraging habitat) at low ambient temperatures and mature coniferous forest (thermal shelter) during thermally stressful conditions, lost less mass in winter and gained more mass in summer.

Conclusions/Significance

This study provides evidence that behavioural responses to temperature have important consequences for seasonal mass change in moose living in the south of their distribution in Norway, and may be a contributing factor to recently observed declines in moose demographic performance. Although the mechanisms that underlie the observed temperature mediated habitat-fitness relationship remain to be tested, physiological state and individual variation in thermal tolerance are likely contributory factors. Climate-related effects on animal behaviour, and subsequently fitness, are expected to intensify as global warming continues.     

Seasonal variations of physiological characteristics and thermal sensation under identical thermal conditions

Seasonal variations of human thermal characteristics were inspected in thermal comfort and when constantly indoors. Metabolic rate, tympanic temperature, skin temperature, body fat, body weight and thermal sensation were measured under identical thermal conditions in a chamber over the course of one year. Experiments were carried out for each subject in both summer and winter. Six subjects were measured 35 times in summer and 45 times in winter. one subject was measured weekly for 14 months. Measurements for analyses were taken 40-60 min after entrance into the chamber. Results revealed the following. 1) For all subjects, the metabolic rate, tympanic temperature and body fat were lower in summer than in winter; thigh skin temperatures were higher in summer than in winter. The averaged individual ratio of seasonal difference was 11.9% for metabolic rate, 14.9% for body fat, 1.8% for thigh temperature and 0.53% for tympanic temperature. Seasonal differences of about 10% in metabolic rate were maintained in this study. 2) Seasonal variations of the variables were examined for phase relationships against the outdoor temperature. 2-1) Metabolic rate, thermal sensation, body weight and body fat changed in reverse phase, whereas skin temperature was in-phase. 2-2) Skin temperature lagged by about one month in both summer and winter. Body fat also lagged by about one month in summer, but corresponded to the phase in winter. Metabolic rates were also in-phase in winter but led about three months in summer. Thermal sensations lagged by about three months in winter but were in-phase in summer. Body weight was in-phase in summer and winter. 2-3) Summer disorders were observed particularly in seasonal variations of metabolic rates, tympanic temperature, skin temperatures, and thermal sensation, thereby suggesting that the effect of temperature exposure was altered by air-conditioner use.     

Decline of a montane Mediterranean pied flycatcher Ficedula hypoleuca population in relation to climate

Certain populations of long‐distance migratory birds are suffering declines, which may be attributed to effects of climate change. In this article, we have analysed a long‐term (1991–2015) data set on a pied flycatcher Ficedula hypoleuca population breeding in nest‐boxes in a Mediterranean montane oak forest, exploring the trends in population size due to changes in nestling recruitment, female survival and female immigration. We have related these changes in population parameters to local climate, winter NAO index and to breeding density. During the last 25 yr the population has declined by half, mainly in association with a decrease in nestling mass and structural size which had repercussions on the probability of nestling recruitment to the population. Lower local nestling recruitment in certain years was linked to lower female immigration rate in the same years. On the other hand, the local survival of females remained stable throughout the study period. Laying date and breeding success were negatively affected by local temperatures while breeding, recruitment rate likewise by minimum temperature prior to breeding in April. As minimum April temperatures have increased across the study period, this may have affected recruitment and immigration rates negatively. On the other hand, tarsus length and body mass of nestlings were positively associated with winter NAO index, pointing to more global climatic links. Moreover, there was also a negative temporal trend in body mass of adults, implying increasingly difficult conditions for breeding. Declining recruit production in the study area could be attributed to a mismatch between the timing of arrival and breeding in the population, and the peak of food availability in this area.     

Expression of biotransformation genes in woodrat (Neotoma) herbivores on novel and ancestral diets: identification of candidate genes responsible for dietary shifts

The ability of herbivores to switch diets is thought to be governed by biotransformation enzymes. To identify potential biotransformation enzymes, we conducted a large-scale study on the expression of biotransformation enzymes in herbivorous woodrats ( Neotoma lepida ). We compared gene expression in a woodrat population from the Great Basin that feeds on the ancestral diet of juniper to one from the Mojave Desert that putatively switched from feeding on juniper to feeding on creosote. Juniper and creosote have notable differences in secondary chemistry, and thus, should require different biotransformation enzymes for detoxification. Individuals from each population were fed juniper and creosote diets separately. After the feeding trials, hepatic mRNA was extracted and hybridized to laboratory rat microarrays. Hybridization of woodrat samples to biotransformation probes on the array was 87%, resulting in a total of 224 biotransformation genes that met quality control standards. Overall, we found large differences in expression of biotransformation genes when woodrats were fed juniper vs. creosote. Mojave woodrats had greater expression of 10× as many biotransformation genes as did Great Basin woodrats on a creosote diet. We identified 24 candidate genes that may be critical in the biotransformation of creosote toxins. Superoxide dismutase, a free radical scavenger, was also expressed to a greater extent by the Mojave woodrats and may be important in controlling oxidative damage during biotransformation. The results are consistent with the hypothesis that biotransformation enzymes limit diet switching and that woodrats in the Mojave have evolved a unique strategy for the biotransformation of creosote toxins.     

Effect of altered ambient temperature on breathing in ponies

The objective was to determine the effect of moderate changes in ambient temperature (TA) on breathing and body temperature in ponies chronically exposed to a TA of 21 degrees C in the summer and 5 degrees C in the winter. Normal (n = 6) and chronic carotid body-denervated (n = 6, 1-2 yr) ponies were studied during 1) winter months over 3-4 days at 5 (control TA) and 23 degrees C and 2) summer months over 2-4 days at 21 (control TA), 30, and 12 degrees C. Neither rectal nor arterial temperature changed with any alteration of TA (P greater than 0.10). Skin temperature (Tsk) always changed by 2-4 degrees C in the same direction as changes in TA (P less than 0.01), and Tsk was the only variable that differed between summer and winter control TA. While breathing room air 24-48 h after TA was altered, pulmonary ventilation (VE) and breathing frequency (f) were approximately 100 and 300%, respectively, above control with elevated TA and approximately 25-50% below control with reduced TA (P less than 0.01). Changes in f were closely related to changes in Tsk. Tidal volume (VT) changed inversely with changes in TA. Generally, while breathing room air, arterial PCO2 (Paco2) did not change from control during the first 48 h of altered TA. In studies when inspired CO2 was elevated VT increased by the same amount at all TA; f increased at low and control TA but decreased at elevated TA; and VE and Paco2 both increased relatively less at elevated TA, but the VE-Paco2 slope was independent of TA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of season, temperature, and body mass on the standard metabolic rate of tegu lizards (Tupinambis merianae)

Abstract This study examined how the standard metabolic rate of tegu lizards, a species that undergoes large ontogenetic changes in body weight with associated changes in life-history traits, is affected by changes in body mass, body temperature, season, and life-history traits. We measured rates of oxygen consumption (Vo(2)) in 90 individuals ranging in body mass from 10.4 g to 3.75 kg at three experimental temperatures (17 degrees , 25 degrees , and 30 degrees C) over the four seasons. We found that standard metabolic rate scaled to the power of 0.84 of body mass at all experimental temperatures in all seasons and that thermal sensitivity of metabolism was relatively low (Q(10) approximately 2.0-2.5) over the range from 17 degrees to 30 degrees C regardless of body size or season. Metabolic rates did vary seasonally, being higher in spring and summer than in autumn and winter at the same temperatures, and this was true regardless of animal size. Finally, in this study, the changes in life-history traits that occurred ontogenetically were not accompanied by significant changes in metabolic rate.     

Correlation of seasonal acclimatization in metabolic enzyme activity with preferred body temperature in the Eastern red spotted newt (Notophthalmus viridescens viridescens)

Eastern red spotted newts, as aquatic adults, are active year round. They are small and easy to handle, and thus lent themselves to a laboratory study of seasonal changes in preferred body temperature and biochemical acclimatization. We collected newts in summer (n=20), late fall (n=10) and winter (n=5). Ten each of the summer and late fall newts were subjected to an aquatic thermal gradient. Summer newts maintained higher cloacal temperatures than late fall newts (26.8+/-0.5 degrees C and 17.2+/-0.4 degrees C, respectively). In addition, the activity of three muscle metabolic enzymes (cytochrome c oxidase (CCO), citrate synthase (CS) and lactate dehydrogenase (LDH)) was studied in all newts collected. Newts compensated for lower late fall and winter temperatures by increasing the activity of CCO during those seasons over that in summer newts at all assay temperatures (8, 16 and 26 degrees C). The activity of CS was greater in winter over summer newts at 8 and 16 degrees C. No seasonal differences in LDH activity were demonstrated. These data in newts indicate that this amphibian modifies some muscle metabolic enzymes in relation to seasonal changes and can modify its behavioral in a way that correlates with those biochemical changes.     

Survey of raccoons on Key Largo, Florida, USA, for Baylisascaris procyonis

Numbers of the endangered Key Largo woodrat (KLWR; Neotoma floridana smalli) have been declining for at least 25 yr. The raccoon (Procyon lotor) roundworm, Baylisascaris procyonis, has been found to have an adverse effect on the survival of Alleghany woodrats (N. magister). High densities of raccoons can exacerbate this problem by increasing the amount of feces containing viable eggs of B. procyonis available to woodrats. In 2002, 64 fecal samples were collected and examined for eggs of B. procyonis from >32 raccoons within the KLWR's known range on Key Largo, Florida, USA. All samples were negative for eggs of B. procyonis. Raccoon density in this area was approximately 0.62 raccoons/ha. Despite this high density of raccoons, B. procyonis does not appear to be a threat to the KLWR population.     

Description and epidemiology of Theileria youngi n. sp. from a northern Californian dusky-footed woodrat (Neotoma Fuscipes) population

An epidemiologic study designed to identify the small mammal reservoir for the zoonotic WA1-type babesial parasite resulted in the discovery of a small, intraerythrocytic piroplasm in smeared blood from dusky-footed woodrats (Neotoma fuscipes) in northern California. The woodrat parasites were isolated and compared to other piroplasm parasites based on their morphology, antigenicity, and genetic characteristics. These studies indicated that the woodrat parasites were not the WA1-type babesial agent but were of the genus Theileria. We accordingly named it Theileria youngi. The prevalence in the woodrat population was high (61%). Infection was unrelated to gender or age of the woodrats. Potential vectors for this tick-transmitted parasite included 3 species of ticks recovered from the woodrats. Dermacentor occidentalis, Ixodes woodi, and Ixodes pacificus. Mostly larval or nymphal stages were recovered, suggesting transstadial transmission is possible. This is the first piroplasm fully characterized from a dusky-footed woodrat.