Understanding the effects of captivity-induced stress on wild-caught animals after their release back into the wild is critical for the long-term success of relocation and reintroduction programs. To date, most of the research on captivity stress has focused on vertebrates, with far less attention paid to invertebrates. Here, we examine the effect of short-term captivity (i.e., up to four days) on self-righting, aggregation, and predator-escape behaviours in wild-caught red sea urchins, Mesocentrotus franciscanus, after their release back into the wild. Aggregation behaviour, which has been linked to feeding in sea urchins, was not affected by handling or captivity. In contrast, the sea urchins that had been handled and released immediately, as well as those that were handled and held captive, took longer to right themselves and were poorer at fleeing from predators than wild, unhandled sea urchins. These results indicate that handling rather than captivity impaired these behaviours in the short term. The duration of captivity did not influence the sea urchin behaviours examined. Longer-term monitoring is needed to establish what the fitness consequences of these short-term behavioural changes might be. Our study nevertheless highlights the importance of considering a suite of responses when examining the effects of capture and captivity. Our findings, which are based on a locally abundant species, can inform translocation efforts aimed at bolstering populations of ecologically similar but depleted invertebrate species to retain or restore important ecosystem functions.

Waterfowl are potential long‐distance dispersal vectors for aquatic microbes such as diatoms, but supporting empirical data are scarce, especially concerning external transport on feathers. We conducted an experiment designed to partially emulate diatom dispersal via adherence to waterfowl, and to evaluate the effects of relative humidity (RH) and exposure time on viability. We dipped individual breast feathers from mallards (Anas platyrhynchos) in a pure culture of the freshwater diatom Nitzschia pusilla Grunow, then, at room temperature (22.7°C), subjected them to one of four contrasting levels of RH (c. 8%, 35%, 70%, 88%) crossed with one of four exposure times (10, 60, 120, 240 min) within a chamber through which air was passed continuously, mimicking light wind that might be experienced by diatoms adhered to subsurface feathers. We then gently placed the feather on sterile growth medium. After 2 weeks, we used spectrofluorometry to detect diatom growth and thus diatom viability. We found that exposure time and RH interacted significantly to affect diatom viability: the negative effect of exposure time was strongest under low RH conditions, but under high RH (88%) the probability of being viable was 0.84 for a 10‐min exposure (95% confidence interval: 0.64–0.94), and 0.45 for 4 hr of exposure (95% confidence interval: 0.18–0.75). We combined our experimental findings with geospatial data to predict the probability of potential dispersal via adherence to mallards throughout Nebraska, South Dakota, and North Dakota, which are situated within the central waterfowl migration flyway in North America, and host important mallard breeding grounds. Using published data about: (1) mallard flight speeds; (2) the geographic distribution of surface waters and of N. pusilla; and (3) vapour pressure deficit (calculated using RH and air temperature) during the months of April and May, our geospatial model predicted high probabilities of potential dispersal, over tens to hundreds of kilometres, among water bodies of the central migration flyway. Taken together, the results of our experiment and geospatial models provide novel insights into ectozoochory of freshwater diatoms, specifically that long‐distance dispersal of diatoms via adherence to waterfowl feathers is highly plausible, particularly during the near‐dawn hours when waterfowl flight activity peaks and vapour pressure deficit is low. Considered alongside previous evidence suggesting successful internal transport by waterfowl, we conclude that, for freshwater diatoms, ectozoochory is likely to be commonplace among waterbodies frequented by waterfowl.

Waterfowl are potential long-distance dispersal vectors for aquatic microbes such as diatoms, but experimental evidence is scarce. We conducted an experiment designed to emulate diatom dispersal via adherence to waterfowl, and to evaluate the effects of humidity and transport duration on potential dispersal success. We dipped individual mallard breast feathers in a pure benthic diatom culture (Nitzschia pusilla Grunow), then subjected them to one of four relative humidity levels (RH; from ca. 8% to 88%) crossed with one of four transport durations (10, 60, 120, 240 minutes) within a chamber through which air was passed continuously, mimicking light wind. We then placed the feather on sterile growth medium. After two weeks we used spectrofluorometry to detect diatom growth and thus diatom viability. A logistic regression on viability revealed a significant interaction between transport duration and RH: the negative effect of duration was strongest under lower RH conditions, but under high RH (88%) the probability of being viable was moderate to high regardless of transport duration. Importantly, even after 4 hours, the probability of being viable was predicted to be 0.45 (95% confidence interval: 0.18 to 0.75). We then placed our findings in the geographic context of the central waterfowl migration flyway in North America, and specifically Nebraska, South Dakota, and North Dakota, for which sufficient data were available to enable geospatial predictions of potential mallard-borne diatom dispersal. Combined with published data about (i) mallard flight speeds, (ii) the geographic distribution of surface waters and of N. pusilla, and (iii) daytime RH during the months of April through June, our model predicted high probabilities of potential dispersal among the region’s suitable water bodies.

No abstract