Mortality of captive black-footed ferrets (Mustela nigripes) at Smithsonian's National Zoological Park, 1989-2004.

Black-footed ferret (Mustela nigripes) mortality was investigated retrospectively based on the pathology records of 107 captive animals held at Smithsonian's National Zoological Park from 1989 to 2004. The majority of deaths in neonates were due to cannibalism (n = 42; 64.6%) and maternal trauma (n = 11; 16.9%); both of these causes of mortality decreased during the study period. Prior to 2001, juvenile mortality was most often caused by gastrointestinal disease (n = 11; 52.4%), including coccidiosis, salmonellosis, and clostridium infection. In 2001, improvements in husbandry, hygiene, and medical treatment led to decreases in juvenile mortality associated with gastrointestinal disease. The most common causes of death in adult ferrets were renal or neoplastic disease. The etiology of the high prevalence of renal disease in the last 4 yr of the study is unknown; it was not associated with increasing age or inbreeding. Improved hygiene and vigilant monitoring for signs of gastrointestinal and renal disease will continue to improve the success of the captive propagation of this species.     

A comparison of trenched plot techniques for partitioning soil respiration

Partitioning the soil surface CO₂ flux (R_S) flux is an important step in understanding ecosystem-level carbon cycling, given that R_S is poorly constrained and its source components may have different sensitivities to climate change. Trenched plots are an inexpensive but labor-intensive method of separating the R_S flux into its root (autotrophic) and soil (heterotrophic) components. This study tested if various methods of plant suppression in trenched plots affected R_S fluxes, quantified the R_S response to soil temperature and moisture changes, and estimated the heterotrophic contribution to R_S. It was performed in a boreal black spruce (Picea mariana) plantation, using a randomized complete block design, during the 2007 and 2008 growing seasons. Trenched plots had significantly lower R_S than control plots, with differences appearing ∼100 days after trenching; spatial variability doubled immediately after trenching but then declined throughout the experiment. Most trenching treatments had significantly lower (by ∼0.5 μmol CO₂ m⁻² s⁻¹) R_S than the controls, and there was no significant difference in R_S among the various trenching treatments. Soil temperature at 2 cm explained more R_S variability than did 10-cm temperature or soil moisture. Temperature sensitivity (Q₁₀) declined in the control plots from ∼2.6 (at 5 °C) to ∼1.6 (at 15 °C); trenched plots values were higher, from 3.1 at 5 °C to 1.9 at 15 °C. We estimated R_S for the study period to be 241 ± 40 g C m⁻², with live roots contributing 64% of R_S after accounting for fine root decay, and 293 g C m⁻² for the entire year. These findings suggest that laborious hand weeding of trenched plot vegetation may be replaced by other methods, facilitating future studies of this large and poorly-understood carbon flux.     

Growth, foliar nutrition and δC responses of red alder (Alnus rubra) to phosphorus additions soon after planting on moist sites

In south-coastal British Columbia, a low availability of phosphorus (P) may limit the early growth of young red alder (Alnus rubra Bong.), even on sites classified as productive for red alder. However, it remains unclear as to what P addition rates best alleviate P deficiencies on such sites and how long effects of P additions on growth persist.We applied P 1-3 months after planting at rates up to 60 g P tree⁻¹ and assessed growth and foliar elemental contents over three growing seasons at three sites with site productivity classed as good for red alder. Foliar δ¹³C was also determined in year 1 in the two sites on Vancouver Island and in year 2 in the site on the British Columbia mainland coast in order to better understand the relationships among foliar nutritional status, leaf water use efficiency (WUE), and growth.P additions at planting significantly increased height (11-15%), diameter (26%) and stem volume (62-64%) through 3 years. Maximum growth rates were achieved at P addition rates of 30 g tree⁻¹ and at foliar P concentrations of 2.2-2.5 g kg⁻¹. Growth did not increase further at addition rates of 60 g P tree⁻¹. Stem growth increases were accompanied by increased individual leaf mass, first-year foliar concentrations of N, P, Ca, Mg, and S, and foliar δ¹³C, the latter suggesting that WUE increased with P additions. Foliar concentrations of P in unfertilized trees were at deficient levels, based on earlier studies, and increases in first-year foliar P concentrations and stem growth through year 3 were consistent with responses in earlier single-tree plot experiments. Longer-term measurements are required to define the duration of growth response to P additions in these otherwise-productive sites.     

Risk from Sirococcus conigenus to understory red pine seedlings in northern Wisconsin

Interest in development of multicohort stands of red pine (Pinus resinosa) in the Great Lakes region of North America prompted an investigation of the potential impact of the shoot blight pathogen Sirococcus conigenus (syn. S. strobilinus) on understory red pine seedlings. In May 2002 and 2003 healthy, 1‐year‐old red pine seedlings were planted in the understory of a maturing red pine plantation in northern Wisconsin in an area with a history of presence of this pathogen. Occurrence of shoot blight symptoms was recorded periodically during the summer, and in each year seedlings were harvested in fall and examined for signs of shoot blight pathogens. By fall 2002 and 2003, respectively, shoot blight incidence was 89% and 98% and most seedlings were dying. Pycnidia with conidia of S. conigenus were present on almost all of the symptomatic seedlings. The conifer shoot blight and canker pathogen Diplodia pinea (syn. Sphaeropsis sapinea) was also detected, though less frequently. Pycnidia of S. conigenus tended to be found more frequently on symptomatic current year's shoots than symptomatic previous year's shoots; the opposite was true for pycnidia of D. pinea. Risk from S. conigenus to understory red pine seedlings should be considered in any plans for development of multicohort red pine stands in areas where the pathogen is present.     

Radial modulus of rupture in radiata pine measured by individual rings

New equipment was developed to measure the strength of individual annual rings in green wood under predominantly tensile stress. This equipment was then used to assess the variation of the radial modulus of rupture (rMOR) in thirty-six 25-year-old radiata pine trees taken from three sites in New Zealand. The rMOR for individual rings ranged from 4.2 to 12.7 MPa and was calculated on the assumption that during bending of the specimens fracture was caused by the tensile force in the radial direction (i.e., perpendicular to the tangential-longitudinal plane). No consistent trends were observed in rMOR from pith to bark; nor was there any evidence of differences between the three sites. However, there was substantial between-tree variability that manifested mainly in different average rMOR values for the trees rather than in variations from pith to bark. These results indicate that there are no concerns with respect to splitting resistance for the juvenile wood of radiata pine. It will be of interest to investigate whether splitting resistance is under genetic control.     

Parasitism of a native Hawaiian stream fish by an introduced nematode increases with declining precipitation across a natural rainfall gradient

Climate change can promote disease emergence if shifting conditions favour infection of native fauna by introduced parasites and pathogens. In Hawai'i, climate warming is predicted to reduce net precipitation and surface flow in streams, which in turn could increase parasitism of native stream fishes by non‐native parasites. In this study, we utilised a natural precipitation gradient across the Hamakua coast on the island of Hawai'i to assess the relationship between precipitation and infection of Awaous stamineus, a native amphidromous goby, by the introduced nematode Camallanus cotti. We found that the abundance, intensity and prevalence of C. cotti in A. stamineus increased with declining rainfall. Our results also show that parasitism tracks precipitation patterns across the archipelago and that parasitism increases even with moderate decreases in rainfall. As the Hamakua coast precipitation gradient represents a proxy for predicted climate‐driven reductions in precipitation, these findings suggest that infection of native Hawaiian fishes by introduced parasites will increase if climate conditions change as expected. Our findings also suggest that parasitism may be exacerbated by other factors that reduce surface flow, including water extraction for agricultural and urban uses. If so, then adaptive management of minimum flow standards in Hawai'i and elsewhere could improve the well‐being of at‐risk native fishes by alleviating parasitism under current and future climate conditions.     

Release of luteinizing hormone in male mice during exposure to females: habituation of the response

Male mice release luteinizing hormone when exposed for a short time to a female. In this experiment, multiple blood samples were withdrawn by atrial cannulas from tethered males during either continuous or intermittent exposure to nonreceptive females. After an immediate, transient release of luteinizing hormone, continuous exposure to the same female was accompanied by only random, spontaneous elevations in plasma levels of this hormone. Successive presentations of the same female at 2-hour intervals elicited gradually diminishing luteinizing hormone responses. Exposing such unresponsive males to novel, diestrous females, however, dramatically stimulated their release of the hormone. These results demonstrate habituation of a socially induced, neuroendocrine response involving reproductive hormones.