Panic at the disco: solar-powered strobe light barriers reduce field incursion by African elephants Loxodonta africana in Chobe District, Botswana

Managing interactions between humans and wild elephants is a complex problem that is increasing as a result of agricultural and urban expansion into and alongside protected areas. Mitigating negative interactions requires the development of new tools to reduce competition and promote coexistence. Many studies have tested various mitigation techniques across elephant ranges in Africa and Asia, with varying levels of success. Recently, strobe lights have been suggested as a potential mitigation strategy in deterring African lions Panthera leo from kraals or bomas, but this technique has to date not been tested to reduce negative human–elephant interactions. Over a 2-year period (November 2016–June 2018), we tested the effectiveness of solar-powered strobe light barriers in deterring African elephants Loxodonta africana, in collaboration with 18 farmers in a community adjacent to the Chobe Forest Reserve and Chobe National Park in northern Botswana. Although elephants were more likely to pass by fields with solar-powered strobe light barriers (which was probably a result of selection bias as we focused on fields that had previously been damaged by elephants), they were less likely to enter these treatment fields than control fields without such barriers. Our findings demonstrate the efficacy of light barriers to reduce negative human–elephant interactions in rural communities.

Units of motor production: Bengalese finches interrupt song within syllables

Birdsong consists of syllables that are separated by silent intervals. Previous work in zebra finches showed that syllables correspond to the smallest motor production units (Cynx, 1990; Franz and Goller, 2002) by inducing song stops using strobe light. In this study, we interrupted the song of six Bengalese finches experimentally with the bird’s own song as auditory stimulus using an interactive playback approach. Five of the tested males interrupted their ongoing vocalizations within syllables (16 instances of induced interrupted syllables) in response to the playback. Additionally, we observed 9 spontaneous interruptions in our control recordings. This study establishes that birds can interrupt ongoing syllables within extremely short latencies in response to an auditory stimulus, and that auditory stimuli interrupt syllables more effectively than visual stimuli. Even if syllables are the functionally stable production units, the ability to disrupt those units differs between species and individuals, indicating various degrees of vocal control.

Philosophical Times and Spaces

In luminist and cinematic registers, the chapter first explicates Deleuze’s complementary chronologics of Aion and Chronos. While durational Aion is the time of luminist glow, flickering Chronos is the time of strobe light: wave and particle. Shifting from time to space, the chapter then addresses Deleuze’s topologics. After introducing the notion of fractal space in terms of Deleuze’s notion of becoming-imperceptible, it delineates, via Leibniz’ images of the baroque house and the camera obscura, Deleuze’s transformation of the spatial dualism of light surface and dark depth into the luminous space of a fractal chiaroscuro, and it shows how Deleuze’s luminous philosophy resonates with Leibniz’ proposition that monads, as points or centres of light, have a luminous nature. After explicating the mathematical concept of the ‘real projective plane,’ the chapter argues that Deleuze’s shift from a Cartesian to a projective topology of thought is fundamental for an understanding of his philosophy.

Behavioural Response of Juvenile Common Carp (Cyprinus carpio) and Juvenile Channel Catfish (Ictalurus punctatus) to Strobe Light

The movement of fish can be regulated by behavioural manipulation through non-physical barrier systems. Aquatic invasive species are becoming one of the major management issues in North America, and threaten native aquatic ecosystems, including freshwater fish. Placements of non-physical barriers in waterways can help disrupt the movement of invasive fish. This study examined the effect of a strobe-light stimulus on the avoidance behaviour of two proxy species, juvenile common carp (Cyprinus carpio) and juvenile channel catfish (Ictalurus punctatus), in a controlled laboratory environment. For each species, three sequential treatments of pre-stimulus, strobe-light stimulus, and post-stimulus for 30 min periods were recorded on acclimated groups of 5 juvenile common carp and 5 juvenile channel catfish using 15 and 13 replicates, respectively. The distribution of juvenile common carp individuals throughout the tank did not change significantly with treatment, nor did cohesive grouping behaviour. Similarly, there were no significant differences across experimental treatments in average location/distance of juvenile channel catfish relative to the strobe light or degree of cohesion in response to the strobe light. Non-physical barriers have been widely reported to vary between species and environmental conditions. These results suggest that strobe lights evoke no avoidance or attractive responses in juvenile common carp and juvenile channel catfish, and will likely not be an effective barrier to inhibit movements of juvenile invasive fishes.

The smoothing of landscapes during snowfall with no wind

ABSTRACTEvery winter, snowy landscapes are smoothed by snow deposition in calm conditions (no wind). In this study, we investigated how vertically falling snow attenuates topographic relief at horizontal scales less than or approximately equal to snow depth (e.g., 0.1–10 m). In a set of three experiments under natural snowfall, we observed the particle-scale mechanisms by which smoothing is achieved, and we examined the cumulative effect at the snowpack scale. The experiments consisted of (a) a strobe-light box for tracking the trajectories of snowflakes at deposition, (b) allowing snow to fall through a narrow gap (40 mm) and examining snow accumulation above and below the gap, and (c) allowing snow to accumulate over a set of artificial surfaces. At the particle scale, we observed mechanisms enhancing (bouncing, rolling, ejection, breakage, creep, metamorphism) and retarding (interlocking, cohesion, adhesion, sintering) the rate of smoothing. The cumulative effect of these mechanisms is found to be driven by snowpack surface curvature, introducing a directional bias in the lateral transport of snow particles. Our findings suggest that better quantification of the mechanisms behind smoothing by snow could provide insights into the evolution of snow depth variability, and snow-vegetation interactions.

Repulsive Effect of Stroboscopic Light Barriers on Native Salmonid (Salmo trutta) and Cyprinid (Pseudochondrostoma duriense and Luciobarbus bocagei) Species of Iberia

A repulsive effect, that some induced primary stimuli, like sound and light, is known to be provoked in fish behavior. In the present study, two strobe light frequencies, 350 flashes/minute and 600 flashes/minute, were tested in laboratorial conditions, using three native freshwater fish species of northern Portugal: Brown trout (Salmo trutta), Northern straight-mouth nase (Pseudochondrostoma duriense) and Iberian barbel (Luciobarbus bocagei). The results showed a differential repulsive behavior of the fish species to light stimulus, and particularly to a frequency of 600 flashes/minute. S. trutta presented the most repulsive behavior, whereas the L. bocagei showed less repulsion to the light stimulus. No relevant differences were found between pre-test and post-assessments, confirming a rapid recovery of natural fish behavior after the deterrent effect. The results highlighted the potential of behavioral barriers, particularly in salmonid streams, based on strobe light stimulus.

The segregation of vocal circuits solves a credit assignment problem associated with multi-objective reinforcement learning

Motor circuits vary in topographic organization, ranging from a coarse relationship between neuron location and function to highly localized regions controlling specific behaviors. For unclear reasons, vocal learning circuits lie at this second extreme: they repeatedly evolved to be spatially segregated from other parts of the motor system. Here we show that spatially segregated motor circuits can solve a specific problem that arises when an animal tries to learn two things at once. We trained songbirds in vocal and place learning paradigms with brief strobe light flashes and noise bursts. Strobe light negatively reinforced place learning but did not affect song syllable learning. Noise bursts positively reinforced place preference but negatively reinforced syllable learning. These double dissociations indicate that vocalization-related reinforcement signals specifically target the vocal motor system, while place-related reinforcement signals specifically target the navigation system. Non-global, target-specific reinforcement signals have established utility in machine implementation of multi-objective learning. In vocal learners, such signals could enable an animal to practice vocalizing as it does other things such as forage for food or learn to walk.