Effects of Artificial Light at Night (ALAN) on European Hedgehog Activity at Supplementary Feeding Stations.

: Artificial light at night (ALAN) can have negative consequences for a wide range of taxa. However, the effects on nocturnal mammals other than bats are poorly understood. A citizen science camera trapping experiment was therefore used to assess the effect of ALAN on the activity of European hedgehogs (Erinaceus europaeus) at supplementary feeding stations in UK gardens. A crossover design was implemented at 33 gardens with two treatments-artificial light and darkness-each of which lasted for one week. The order of treatment depended on the existing lighting regime at the feeding station: dark treatments were applied first at dark feeding stations, whereas light treatments were used first where the station was already illuminated. Although temporal changes in activity patterns in response to the treatments were noted in some individuals, the direction of the effects was not consistent. Similarly, there was no overall impact of ALAN on the presence or feeding activities of hedgehogs in gardens where supplementary feeding stations were present. These findings are somewhat reassuring insofar as they demonstrate no net negative effect on a species thought to be in decline, in scenarios where the animals are already habituated to supplementary feeding. However, further research is needed to examine long-term effects and the effects of lighting on hedgehog prey, reproductive success and predation risk.

Unintentional rewilding: lessons for trophic rewilding from other forms of species introductions.

Trophic rewilding involves adding species into ecosystems to restore extinct, top-down interactions, but limited quantitative data have prevented a systematic attempt to quantify its outcomes. Here, we exploit species introductions that have occurred for purposes other than restoration to inform trophic rewilding. We compiled 51 studies with 158 different responses of lower trophic levels to a species introduction that restored an extinct interaction, whether it intended to do so or not. Unintentional introductions were compared with checklists of extinct animals to identify potential analogues. Using the latest meta-analysis techniques, we found that the few cases of intentional rewilding had similar effects to unintentional rewilding, though there were large taxonomic and geographical biases. We also tested predictions from studies on trophic cascades about the factors that should influence rewilding. Unintentional rewilding was stronger where introduced consumers were non-invasive, but there was no effect of time that compared sites differed in introduction status, latitude or coevolution of responses with a taxonomically related analogue. Our study now shows that rewilding can reinstate extinct trophic interactions and highlights remaining data gaps that need closure to restore ecosystems across larger scales than has been previously possible.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.

Mussels can both outweigh and interact with the effects of terrestrial to freshwater resource subsidies on littoral benthic communities.

Litterfall is an important resource subsidy for lake ecosystems that primarily accumulates in littoral zones. Bivalves are abundant within littoral zones and may modify the effects of terrestrial resource subsidies through trophic interactions and engineering their surrounding habitat. Leaf inputs to lakes and freshwater mussel abundances are changing throughout the boreal ecoregion so we set out to investigate how the co-occurring benthic community might respond. We set up an in situ mesocosm experiment in Ramsey Lake, Sudbury, ON, Canada. Mesocosms contained sediments of either 5% or 35% terrestrial organic matter (tOM), into which we placed mussels (Elliptio complanata) at differing densities (0, 0.4 and 2musselsm-2, with a sham mussel treatment at 0.4musselsm-2). Over one month we recorded the sediment chemistry (dissolved organic carbon, nitrogen and phosphorus), littoral organisms (benthic algae and zooplankton) and mussel growth. At high mussel densities we recorded a 90%, 80%, 45% and 40% reduction in phosphorus, dissolved organic carbon, nitrogen and benthic diatoms, respectively, whereas at low mussel densities we observed a 3-fold increase in zooplankton. We discuss that these results were caused by a combination of bioturbation and trophic interactions. Benthic diatom concentrations were also reduced by 20% in sediments of 35% tOM, likely due to shading and competition with bacteria. Mussel growth increased at high mussel densities but was offset at high tOM, likely due to the organic matter interfering with filter feeding. Our results suggest that mussels can alter the geochemical composition of sediments and abundances of associated littoral organisms, in some cases regardless of tOM quantity. Therefore, the dominant top-down control exerted by freshwater mussels may outweigh bottom-up effects of tOM additions. Generally, our study reveals the importance of considering dominant species when studying the effects of cross-ecosystem resource fluxes.

Predicting metabolic rate across walking speed: one fit for all body sizes?

We formulated a "one-size-fits-all" model that predicts the energy requirements of level human walking from height, weight, and walking speed. Our three-component model theorizes that the energy expended per kilogram per stride is independent of stature at mechanically equivalent walking speeds. We measured steady-state rates of oxygen uptake of 78 subjects who spanned a nearly twofold range of statures (1.07-2.11 m) and sevenfold range of body masses (16-112 kg) at treadmill speeds from 0.4 to 1.9 m/s. We tested the size independence of the model by deriving best-fit equations in the form of the model on four stature groups (n ≥ 15): short, moderately short, moderately tall, and tall. The mean walking metabolic rates predicted by these four independently derived equations for the same set of reference subjects (n = 16; stature range: 1.30-1.90 m) agreed with one another to within an average of 5.2 ± 3.7% at the four intermediate speeds in our protocol. We next evaluated the model's gross predictive accuracy by dividing our 78 subjects into 39 stature-matched pairs of experimental and validation group subjects. The model best-fit equation derived on the experimental group subjects predicted the walking metabolic rates of the validation group subjects to within an average of 8.1 ± 6.7% (R(2) = 0.90; standard error of estimate = 1.34 ml O2·kg(-1)·min(-1)). The predictive error of the American College of Sports Medicine equation (18.0 ± 13.1%), which does not include stature as a predictor, was more than twice as large for the same subject group. We conclude that the energy cost of level human walking can be accurately predicted from height, weight, and walking speed.

Leptin-sensitive neurons in the arcuate nuclei contribute to endogenous feeding rhythms.

Neural sites that interact with the suprachiasmatic nuclei (SCN) to generate rhythms of unrestricted feeding remain unknown. We used the targeted toxin, leptin conjugated to saporin (Lep-SAP), to examine the importance of leptin receptor-B (LepR-B)-expressing neurons in the arcuate nucleus (Arc) for generation of circadian feeding rhythms. Rats given Arc Lep-SAP injections were initially hyperphagic and rapidly became obese (the "dynamic phase" of weight gain). During this phase, Lep-SAP rats were arrhythmic under 12:12-h light-dark (LD) conditions, consuming 59% of their total daily intake during the daytime, compared with 36% in blank-SAP (B-SAP) controls. Lep-SAP rats were also arrhythmic in continuous dark (DD), while significant circadian feeding rhythms were detected in all B-SAP controls. Approximately 8 wk after injection, Lep-SAP rats remained obese but transitioned into a "static phase" of weight gain marked by attenuation of their hyperphagia and rate of weight gain. In this phase, Arc Lep-SAP rats exhibited circadian feeding rhythms under LD conditions, but were arrhythmic in continuous light (LL) and DD. Lep-SAP injections into the ventromedial hypothalamic nucleus did not cause hyperphagia, obesity, or arrhythmic feeding in either LD or DD. Electrolytic lesion of the SCN produced feeding arrhythmia in DD but not hyperphagia or obesity. Results suggest that both Arc Lep-SAP neurons and SCN are required for generation of feeding rhythms entrained to photic cues, while also revealing an essential role for the Arc in maintaining circadian rhythms of ad libitum feeding independent of light entrainment.

Using explicit instruction to teach science descriptors to students with autism spectrum disorder.

Science content is one area of general curriculum access that needs more investigation. Explicit instruction is effective for teaching students with high incidence disabilities a variety of skills, including science content. In this study, we taught three elementary aged students with autism spectrum disorder to acquire science descriptors (e.g., wet) and then generalization to novel objects, pictures, and within a science inquiry lesson via explicit instruction. A multiple probe across behaviors with concurrent replication across participants design measured the effects of the intervention. All three participants met criterion, some were able to generalize to novel objects, pictures, and objects within science inquiry lesson. Outcomes are discussed from the perspective of implications for practice and future research investigations.

The mass-specific energy cost of human walking is set by stature.

The metabolic and mechanical requirements of walking are considered to be of fundamental importance to the health, physiological function and even the evolution of modern humans. Although walking energy expenditure and gait mechanics are clearly linked, a direct quantitative relationship has not emerged in more than a century of formal investigation. Here, on the basis of previous observations that children and smaller adult walkers expend more energy on a per kilogram basis than larger ones do, and the theory of dynamic similarity, we hypothesized that body length (or stature, L(b)) explains the apparent body-size dependency of human walking economy. We measured metabolic rates and gait mechanics at six speeds from 0.4 to 1.9 m s(-1) in 48 human subjects who varied by a factor of 1.5 in stature and approximately six in both age and body mass. In accordance with theoretical expectation, we found the most economical walking speeds measured (J kg(-1) m(-1)) to be dynamically equivalent (i.e. similar U, where U=velocity(2)/gravity · leg length) among smaller and larger individuals. At these speeds, stride lengths were directly proportional to stature whereas the metabolic cost per stride was largely invariant (2.74±0.12 J kg(-1) stride(-1)). The tight coupling of stature, gait mechanics and metabolic energy expenditure resulted in an inverse relationship between mass-specific transport costs and stature (E(trans)/M(b)∝L(b)(-0.95), J kg(-1) m(-1)). We conclude that humans spanning a broad range of ages, statures and masses incur the same mass-specific metabolic cost to walk a horizontal distance equal to their stature.

Assessing the metabolic cost of walking: the influence of baseline subtractions.

Partitioning locomotor metabolic rates into resting and locomotor components is a common practice that has both basic and applied value. Here, we evaluated the quantitative influence of the specific baseline value subtracted (quiet standing vs. resting metabolic rates) from the gross metabolic rates measured during walking. We quantified resting, standing and gross metabolic rates during horizontal treadmill walking at six speeds from 0.2 through 1.9 m*s(-1) in 6 healthy, adult subjects. We found that standing metabolic rates were significantly greater than resting values (1.25 +/- 0.03 vs. 1.08 +/- 0.02 W*kg(-1)) and that both constituted large fractions of the gross metabolic rate while walking at all speeds examined (range 16-58%). Differences in the respective net metabolic rates obtained by subtracting standing vs. resting values differed most at the slowest speed measured (16.0% at 0.2 m*s(-1)) and least at the fastest one (2.9% at 1.9 m*s(-1)). Standing metabolic rates, like walking metabolic rates, include the metabolic cost of muscular activation for balance and maintaining an upright posture. Therefore, the net metabolic rates determined by subtracting standing from gross rates underestimate the total muscular costs that walking requires. We suggest that the net walking metabolic rates obtained by subtracting resting metabolic rate values are more representative of the total metabolic energy that walking requires.