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A northern population of snapping turtles (Chelydra serpentina) centred around Lake Sasajewun in the Wildlife Research Area in Algonquin Park, Ontario, has been studied and individually marked since 1972. From 1972 to 1985, annual mortality and survivorship of adult females had been estimated at 1 and 96.6%, respectively, and only six dead turtles were found. Lake Sasajewun's population of C. serpentina was estimated in 1978–1979 and 1984–1985 at 38 and 47 adults, respectively. From 1976 to 1987, total number of nests found in the study area remained fairly constant and there were no significant changes in mean clutch size, mean clutch mass, or mean egg mass. On the main nest site, recruitment from 1976 to 1987 was 1.15 (1.8%) new females per year. From 1987 to 1989, we found 34 dead adult snapping turtles in the Wildlife Research Area. Observations of freshly dead animals indicated that most were killed by otters (Lutra canadensis) during the turtles' winter hibernation. A few uninjured turtles also died of septicemia in early spring shortly after emerging from hibernation. The estimated number of adults in Lake Sasajewun was 31 in 1988–1989, and the minimum number of adult residents known to be alive in the lake dropped from 47 in 1986 to 16 in 1989. In 1986 and 1987, annual adult female survivorship was estimated at 80 and 55%, respectively, and estimated numbers of nesting females declined from 82 in 1986 to 71 and 55 in 1987 and 1988, respectively. The actual number of nests found declined by 38 and 20% over the same periods. Although no significant differences occurred in mean egg mass or mean clutch size between 1987 and 1989 and earlier years, the mean clutch mass in 1988 was larger than in 1977 or 1978. This difference appeared to be due to a gradual increase in the mean age and body size of breeding females rather than to density-dependent changes. Recruitment into the adult breeding female population in 1987–1989 remained less than two individuals per year. Hatchling survival and number of juveniles were low throughout the study. Our observations support the view that populations of species with high, stochastic juvenile mortality and long adult life spans may be decimated quickly by increased mortality of adult animals, particularly if numbers of juveniles and immigrants are low. Recovery of such populations should be very slow because of a lack of effective density-dependent response in reproduction and recruitment.

Objective To measure the extent to which the provision of mammograms was impacted by the COVID‐19 pandemic and surrounding guidelines. Data Sources De‐identified summary data derived from medical claims and eligibility files were provided by Independence Blue Cross for women receiving mammograms. Study Design We used a difference‐in‐differences approach to characterize the change in mammograms performed over time and a queueing formula to estimate the time to clear the queue of missed mammograms. Data Collection We used data from the first 30 weeks of each year from 2018 to 2020. Principal Findings Over the 20 weeks following March 11, 2020, the volume of screening mammograms and diagnostic mammograms fell by 58% and 38% of expected levels, on average. Lowest volumes were observed in week 15 (April 8 to 14), when screening and diagnostic mammograms fell by 99% and 74%, respectively. Volumes began to rebound in week 19 (May), with diagnostic mammograms reaching levels to similar to previous years’ and screening mammograms remaining 14% below expectations. We estimate it will take a minimum of 22 weeks to clear the queue of missed mammograms in our study sample. Conclusions The provision of mammograms has been significantly disrupted due to the COVID‐19 pandemic.

Clutches of six female snapping turtles (Chelydra serpentina) each were distributed among six incubators set at one of three constant temperatures (22.0, 25.6, and 28.6 °C) in either a wet (−100 kPa) or a dry (−500 kPa) vermiculite substrate. We tested for influences of egg mass, clutch, and incubation temperature and moisture on survival of embryos and hatchlings, on size at hatching, and on rate of post-hatching growth over 7 months. Intraclutch variation in egg mass had no effect on embryonic mortality. Mass at hatching was correlated with egg mass, but neither variable was related significantly to post-hatching survival or rate of growth. Eggs incubated at the highest temperature produced smaller hatchlings which subsequently grew more slowly than those from eggs incubated at the low and intermediate temperatures. Eggs incubated at the intermediate temperature produced larger turtles at 7 months post-hatching than did eggs incubated at the low or high temperatures. Eggs incubated in wet substrates produced larger hatchlings than those in dry substrates, but post-hatching growth rates were independent of these effects of moisture. Eggs incubated at the two extreme temperatures produced mostly females; those at 25.6 °C produced only males. Interclutch variation was significant for egg mass, mass at hatching, and survival of embryos, and was the most important influence on variation in post-hatching rates of growth. These results indicate that egg size and size at hatching may not be useful indicators of intraspecific variation in egg quality or post-hatching success in turtles, unless differences among clutches and embryonic thermal experience are also considered, particularly in relation to parental investment in the amount, quality, and apportionment of the egg's yolk.

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Playback of recorded songs of white-throated sparrows (Zonotrichia albicollis) to territorial males elicited a stronger response to songs of strangers than to songs of territorial neighbors. Responses to a bird's own song were intermediate. All test songs were played on the territorial boundary adjacent to the neighbor used in the experiment. Peak of response by song occurred in the 1st min after cessation of playback.Two sets of experiments, 3 weeks apart, showed waning of response to neighbors' songs, but no change in response to strangers' songs. This waning progressed steadily over a 6-week period. No decrement was observed when four periods of playback of a neighbor's song were presented within 1 h. Response to a neighbor's song within a 1-h sequence was independent of whether the preceding playback was of a stranger or neighbor. This indicated that discrimination occurred after only one or two renditions of a song.The mechanism of differential response is interpreted as habituation to neighbors' songs. Adaptiveness of this behavior is discussed.

With 5 figures in the text)We tested the hypothesis that larger egg and hatchling sizes in the snapping turtle confer posthatching advantages, by comparing the growth rates and survival of hatchlings from different thermal and hydric environments during embryonic development. We also tested for sex-specific differences in survival and growth, two indices of hatchling fitness, as predicted by the Charnov & Bull (1977) model of environmental sex determination (ESD). In addition, we examined interclutch and interpopulation variability in the responses of embryos and hatchlings to incubation conditions. Eggs of 21 clutches from four Ontario populations were incubated at 22,0,25,5 or 29·3°C in a dry (-350 kPa) or wet (-150 kPa) vermiculite substrate, and hatchling survival and growth in the laboratory were monitored for 11 months. Initial egg mass and substrate moisture were positively correlated with mass at hatching, but did not affect hatching success, posthatching growth or posthatching survival. Initially heavier hatchlings were more likely to survive, but did not grow more quickly. The effects of incubation environment and hatchling mass were not consistent among clutches or populations. Intermediate incubation temperatures produced mostly males, with higher embryo and hatchling survival, as well as posthatching growth, than the mostly females from the extreme temperatures. These results support the Charnov-Bull model. Embryo and hatchling mortality and deformities were higher in clutches from two populations which are contaminated with organochlorine toxins. Interclutch differences were significant for all variables, even when initial egg or hatchling sizes were considered. Hatchlings from the population near the northern limit of the species' range grew the slowest. These results indicate that hatchling size cannot be used as an index of hatchling quality or posthatching success, unless interclutch and interpopulation variation are taken into account.

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