Converting predation cues into conservation tools: The effect of light on mouse foraging behaviour

Prey face a conflict between acquiring energy and avoiding predators and use both direct and indirect cues to assess predation risk. Illumination, an indirect cue, influences nocturnal rodent foraging behaviour. New Zealand holds no native rodent species but has introduced mice (Mus musculus) that severely impair native biodiversity. We used Giving-Up Densities (GUDs) and observations of foraging frequency and duration to assess if artificial light induces risk avoidance behaviour in mice and could limit their activity. We found both captive (wild strain) mice in outdoor pens and wild mice within a pest fenced sanctuary (Maungatautari, New Zealand) displayed avoidance behaviour in response to illumination. In captivity, total foraging effort was similar across lit and unlit pens but mice displayed a strong preference for removing seeds from dark control areas (mean: 15.33 SD: +/-11.64 per 3.5 hours) over illuminated areas (2.00 +/-3.44). Wild mice also removed fewer seeds from illuminated areas (0.42 +/-1.00 per 12 hours) compared to controls (6.67 +/-9.20). Captive mice spent less than 1.0% of available time at illuminated areas, versus 11.3% at controls; visited the lit areas less than control areas (12.00 +/- 9.77 versus 29.00 +/-21.58 visits respectively); and spent less time per visit at illuminated versus control areas (8.17 +/-7.83 versus 44.83 +/-87.52 seconds per visit respectively). Illumination could provide protection at ecologically sensitive sites, damaged exclusion fences awaiting repair, fence terminus zones of peninsula sanctuaries and shipping docks that service offshore islands. We promote the hypothesis that the tendency of mice to avoid illumination could be a useful conservation tool, and advance knowledge of risk assessment and foraging under perceived danger

Amplitudes on abelian categories

The use of persistent homology in applications is justified by the validity of certain stability results. At the core of such results is a notion of distance between the invariants that one associates to data sets. While such distances are well-understood in the one-parameter case, the situation for multiparameter persistence modules is more challenging, since there exists no generalisation of the barcode. Here we introduce a general framework to study stability questions in multiparameter persistence. We introduce amplitudes -- invariants that arise from assigning a non-negative real number to each persistence module, and which are monotone and subadditive in an appropriate sense -- and then study different ways to associate distances to such invariants. Our framework is very comprehensive, as many different invariants that have been introduced in the Topological Data Analysis literature are examples of amplitudes, and furthermore many known distances for multiparameter persistence can be shown to be distances from amplitudes. Finally, we show how our framework can be used to prove new stability results.Comment: 49 pages, major revisions throughout; added section on preliminaries, reorganised/improved main sections in the paper, removed discussion about general finitely encoded module

Using five-minute bird counts to study magpie (Gymnorhina tibicen) impacts on other birds in New Zealand

We used five-minute bird counts to investigate whether introduced Australian magpies (Gymnorhina tibicen) influence the abundance of other birds in rural New Zealand. Over 3 years, magpies were removed from five c. 900-ha study blocks, one in each of Northland, Waikato, Bay of Plenty, Wellington and Southland. Birds were counted in both the treatment blocks and paired non-treatment blocks for the 3 years of removal and also 1 year before. To minimise problems raised elsewhere with index counts we (1) selected treatment blocks and count stations using randomisation procedures, (2) used trained observers who spent equal time in paired treatment and non-treatment blocks, and (3) counted all blocks at the same time of year and only in good weather. On average, 548 magpies were removed from each treatment block each year, with magpie counts reduced by 76% relative to non-treatment blocks. Our results suggest magpies may restrict the movements of some birds (including kererū and tūī) in rural areas, but are less important than pest mammals at limiting population abundance at a landscape scale. We submit that five-minute bird counts were appropriate for our objectives, but that more research to examine their relationship to absolute densities is needed

Considerations on the use of video playbacks as visual stimuli: The Lisbon workshop consensus

This paper is the consensus of a workshop that critically evaluated the utility and problems of video playbacks as stimuli in studies of visual behavior. We suggest that video playback is probably suitable for studying motion, shape, texture, size, and brightness. Studying color is problematic because video systems are specifically designed for humans. Any difference in color perception must lead to a different color sensation in most animals. Another potentially problematic limitation of video images is that they lack depth cues derived from stereopsis, accommodation, and motion parallax. Nonetheless, when used appropriately, video playback allows an unprecedented range of questions in visual communication to be addressed. It is important to note that most of the potential limitations of video playback are not unique to this technique but are relevant to all studies of visual signaling in animals

Can redirected aggression explain interspecific attacks by Australian magpies on other birds?

Attacks by participants of conflicts against a third party are referred to as redirected aggression. Usually the third party is a conspecific — few documented cases of redirected aggression against other species exist. The Australian magpie (Gymnorhina tibicen), however, often attacks other species; the reasons for attacks are largely unknown. Some attacks occur after territorial disputes with conspecifics, suggesting that attacks are the result of redirected aggression. We subjected eight Australian magpie groups to simulated territorial intrusions. In one treatment an Australian magpie and rock dove (Columba livia) were presented in cages next to one another (5 m apart) on the territory for 30 min; the Australian magpie decoy was then covered and aggressive responses toward the rock dove by residents were recorded for a further 30 min (Treatment 1). Two additional treatments were presented in an identical manner on each territory where both decoys were either Australian magpies (Treatment 2) or rock doves (Treatment 3). We predicted that if Australian magpies regularly redirect aggression onto benign species after conspecific territorial intrusions, attack rates on the rock dove decoy in Treatment 1 would be higher than attack rates on the rock dove decoy in Treatment 3. Residents were seldom recorded close (<1 m) and not seen attacking rock dove decoys during tests. In contrast, Australian magpie decoys were often approached and attacked by residents. After a decoy was covered (following the first 30 min phase), residents spent little time in close proximity (on cage, <0.3 m, or 0.3-1 m) to the rock dove decoy in either Treatment 1 or Treatment 3; in contrast, residents were often recorded close to the Australian magpie decoy in Treatment 2. We found no evidence that Australian magpies redirect aggression onto other birds after territorial intrusions. The true proportion of territorial disputes leading to redirected attacks may be small, or only occur under highly specific contexts

Detection of wild house mice and other small mammals up trees and on the ground in New Zealand native forest

Determining pest mammal impacts and abundance in forests requires an understanding of how target species use vegetation compared with the ground. We used a novel device combining footprint tracking with bite detection to survey for mammals at four levels in New Zealand forests that had house mice (Mus musculus) alone, and all widespread New Zealand mammals, including house mice, ship rats (Rattus rattus) and brushtail possums (Trichosurus vulpecula). When alone, house mice were detected at 93%, 35%, 17% and 0% of devices on the ground, in shrubs, in the subcanopy and canopy, respectively, but in a pilot study at one site were detected 11 m above ground. When all small pest mammals were present, house mice were scarce and none were detected up trees. Ship rats and possums were detected mostly on the ground, but also at all surveyed heights. The study confirms that mice, ship rats and possums are all potential above-ground predators, but suggests that targeting them for control and monitoring can reasonably be undertaken on the ground