Response of secondary production by macroinvertebrates to large wood addition in three Michigan streams

1. We measured responses in macroinvertebrate secondary production after large wood additions to three forested headwater streams in the Upper Peninsula of Michigan. These streams had fine‐grained sediments and low retention capacity due to low amounts of in‐channel wood from a legacy of past logging. We predicted that wood addition would increase macroinvertebrate secondary production by increasing exposed coarse substrate and retention of organic matter. 2. Large wood (25 logs) was added haphazardly to a 100‐m reach in each stream, and a 100‐m upstream reach served as control; each reach was sampled monthly, 1 year before and 2 years after wood addition (i.e. BACI design). Macroinvertebrate secondary production was measured 1 year after wood addition in two habitat types: inorganic sediments of the main channel and debris accumulations of leaf litter and small wood. 3. Overall macroinvertebrate production did not change significantly because each stream responded differently to wood addition. Production increased by 22% in the main‐channel of one stream, and showed insignificant changes in the other two streams compared to values before wood addition. Changes in main‐channel macroinvertebrate production were related to small changes in substrate composition, which probably affected habitat and periphyton abundance. Macroinvertebrate production was much greater in debris accumulations than in the main‐channel, indicating the potential for increased retention of leaf litter to increase overall macroinvertebrate production, especially in autumn. 4. Surrounding land use, substrate composition, temperature and method of log placement are variables that interact to influence the response of stream biota to wood additions. In most studies, wood additions occur in altered catchments, are rarely monitored, and secondary production is not a common metric. Our results suggest that the time required for measurable changes in geomorphology, organic matter retention, or invertebrate production is likely to take years to achieve, so monitoring should span more than 5 years, and ecosystem metrics, such as macroinvertebrate secondary production, should be incorporated into restoration monitoring programs.     

Digital Photography Improves Consistency and Accuracy of Bat Counts in Hibernacula

ABSTRACT The size and distribution of measurement errors associated with major techniques for estimating numbers of hibernating bats are unstudied, although this is the principle method of enumerating several endangered bat species. However, decisions concerning the listing status of a species under the Endangered Species Act require consistent and accurate estimation of population size and trends. Recent advances in digital photography have improved the ability to produce a quantitative record of the numbers of bats in hibernacula. We surveyed clusters of Indiana bats in a hibernaculum and compared results from counts of digital photographs of clusters to results from 4 variations of visual estimation. We counted bats in photographs using Geographic Information System digitization over the photograph. Total counts from 2 sets of photographs varied by <1.5%. Nonphotographic estimation techniques varied from 76% to 142% of counts from photographs for clusters for which estimation (rather than counting) was used. Where feasible, photography can improve status and trend information for species of concern, permitting more timely and specific management actions.     

Basin-Scale Surveys of Stream-Associated Amphibians in Intensively Managed Forests

Abstract: Conservation and management of native species on landscapes managed for intensive wood production represents an ongoing challenge to forest managers. Previous research suggests that impacts of forest practices on stream-associated amphibians (SAA; giant [Dicamptodon spp.], torrent [Rhyacotriton spp.], and plethodontid [Plethodon spp.] salamanders and coastal tailed frogs [Ascaphus truei]) in Oregon and Washington, USA, vary spatially and temporally as a result of biotic and abiotic factors, some of which can be influenced by management treatments. Although individual harvest units can encompass multiple stream reaches and entire second-order basins, nearly all published research studies used stream reaches of various lengths as sample units. To address this discrepancy between research and operational scales, we sampled first-, second-, and third-order streams in 70 randomly selected third-order basins in Oregon and Washington in 2007 and 2008 to estimate detection and occupancy parameters for SAA and to develop basin-level density estimates for different species and genera. We estimated occupancy probabilities of 0.99 (95% CL = 0.96–1.00) for torrent and giant salamanders, 0.93 (95% CL = 0.76–0.92) for Dunn's salamanders (Plethodon dunni), and 0.60 (95% CL = 0.46–0.72) for tailed frogs. Our estimates can be compared with estimates for unmanaged third-order basins in Oregon and Washington to provide a relative measure of potential impacts of forest management on these taxa. In addition, our estimates provide baseline information with which to assess potential effects of future environmental changes on the 4 genera.     

Survival and Cause-Specific Mortality of Red Foxes in Agricultural and Urban Areas of Illinois

Abstract: Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaike's Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0-20%) and high (80-100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40-70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May-Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.     

Oxygen Uptake In Cysts and Trophozoites of Giardia Lamblia

ABSTRACT. Oxygen uptake in cysts and trophozoites of the parasitic protozoan Giardia lamblia was examined. Both showed oxygen uptake activity, but that of cysts was only 10% to 20% that of trophozoites. Oxygen dependence of oxygen uptake in cysts and trophozoites showed oxygen maxima above which oxygen uptake decreased. the oxygen concentration at which the oxygen uptake rate was greatest was higher for trophozoites than for cysts. the effect of various inhibitors on cyst and trophozoithe oxygen uptake suggested that flavoproteins and quinones play some role in oxygen uptake. the substrate specificities and the effect of inhibitors on G. lamblia trophozoites were similar to those observed for G. muris. Metronidazole, the drug most commonly used in treatment of giardiasis, inhibited oxygen uptake and motility in trophozoites; however, it had no obvious effect on either oxygen uptake or excystation in cysts. Menadione, a redox cycling naphthaquinone, first stimulated, then completely inhibited, oxygen uptake in cysts and trophozoites; a complete loss of cyst viability and trophozoite motility was also observed. the effect of menadione on G. Iamblia may indicate that redox cycling compounds have potential as chemotherapeutic agents for the treatment of giardiasis.