Carnivorous predators are difficult to detect using conventional survey methods, especially at low levels of abundance. The introduced red fox (Vulpes vulpes) in Australia is monitored to determine the effectiveness of control programs, but assessing population parameters such as abundance and recruitment is difficult. We carried out a feasibility study to determine the effectiveness of using faecal DNA analysis methods to identify individual foxes and to assess abundance before and after lethal control. Fox faeces were collected in two sampling periods over four separate transects, and genotyped at five microsatellite loci. Two transects were subject to lethal control between collection periods. DNA was extracted from 170 fox faeces and, in total, 54 unique genotypes were identified. Fifteen biopsy genotypes from 30 foxes killed during lethal control were detected among the faecal genotypes. Overall, a similar number of genotypes were detected in both sampling periods. The number of individuals sampled in both periods was low (n = 6) and new individuals (n = 24) were detected in the second collection period. We were also able to detect animals that avoided lethal control, and movement of individuals between transects. The ability to identify individual foxes using these DNA techniques highlighted the shortcomings of the sample design, in particular the spatial scale and distances between transects. This study shows that noninvasive DNA sampling can provide valuable insight into pre and post fox abundance in relation to lethal control, individual behaviour and movement, as well as sample design. The information gained from this study will contribute to the design of future studies and, ultimately, control strategies.

Meat-based baits are currently used for the control of the exotic red fox (Vulpes vulpes) in south-eastern Australia. Thirty-one quadrupedal endemic mammals are considered to be potentially bait consuming (PBC) and may be exposed to bait toxicants. Mechanical toxicant ejectors may be more selective if some PBC species cannot apply enough upward force to trigger them. A simple relationship between body mass and pulling force was sought to enable estimates of ejector specificity to be made. The pulling force applied to ejector baits was measured for the red fox and six endemic mammals. The relationship between body mass and pulling force was highly significant (P < 0.001) and the resulting regression equation was used to estimate the highest pulling forces for 31 quadrupedal mammals based upon the largest body mass recorded for each species. In a sample of 640 foxes, taken by a range of methods in south-eastern Australia, the lowest adult body mass detected from January to September was 3 kg and declined only when cubs were present in the population from October to December. An ejector trigger force of 26.46 N was estimated to allow foxes weighing >3 kg to trigger the device, while eliminating exposure of 26 of the 31 PBC mammals. Appropriate toxicant selection and dose rates may ensure that four out of five susceptible mammals are less likely to be affected by unwanted exposure.

No abstract

No abstract

We used video digitization and playback of courting male Schizocosa ocreata wolf spiders to examine responses of intended receivers and eavesdroppers viewing manipulated spider color displayed against background treatments of complex litter with different chromatic contrast. Intended receivers (female S. ocreata) were more likely to detect males with higher background intensity contrast, while a different pattern for receptivity suggests chromatic contrast matters more for mate recognition. Social eavesdroppers (conspecific males) were similar but had a significant interaction of spider color x background, suggesting possible differences in color perception between sexes. Interceptive eavesdroppers (predators) differed across taxa in some respects but were similar in others. Vertebrates (toads) were quicker to orient than invertebrates (spider predators). Toads took longer to respond to control spiders on complex color backgrounds but were quicker with the same spider against complex greyscale backgrounds. Color differences among prey stimuli appear to be less important than contrast for both toads and wolf spiders with dichromatic vision. However, color of the prey spider stimulus matters more for jumping spiders with trichromatic vision, as they respond more quickly to natural color and RGB average color than gray monochrome stimuli. Analyses of chromatic and luminance intensity contrast values for spiders and backgrounds suggest that for both intended female receivers and eavesdroppers, intensity and chromatic contrast influence detection and mate recognition in complex and subtle ways. These results support the hypothesis that receivers with different visual sensory capacities vary in response to color and contrast of courting male spiders against complex backgrounds.

During metamorphosis from ammocoete to macrophthalmia in the southern hemisphere lamprey, Geotria australis Gray, 2 bluegreen dorso-lateral stripes develop along the length of the body. These stripes are retained during the marine parasitic feeding stage and are conspicuous when the adults enter fresh water at the beginning of the spawning migration. They disappear as the upstream migration progresses. The blue-green coloration is present in the epidermal mucous layer and results from the deposition of biliverdin, a bile pigment produced as a breakdown product of haemoglobin. Liver colour changes during the upstream spawning migration. At the beginning of the migration liver colour is predominantly brown or brick-red, and livers contain the bile pigment bilirubin. Lampreys collected 50 km from the sea had predominantly green livers owing to the presence of the bile pigment biliverdin, and gonad development had not increased from that observed at the beginning of the spawning migration. Pouched males contained dark green livers with biliverdin as the predominant pigment.