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“Infrared Antenna-like Structures in Mammalian Fur”, Baker 2021

“Infrared antenna-like structures in mammalian fur”⁠, Ian M. Baker (2021-12-08; similar):

Many small animals, including shrews, most rodents and some marsupials, have fur composed of at least 4 types of hair, all with distinctive and complex anatomy. A ubiquitous and unexplained feature is periodic, internal banding with spacing in the 6–12 µm range that hints at an underlying infrared function.

One bristle-like form, called guard hair⁠, has the correct shape and internal periodic patterns to function as an infrared antenna. Optical analysis of guard hair from a wide range of species shows precise tuning to the optimum wavelength for thermal imaging.

For heavily predated, nocturnal animals the ability to sense local infrared sources has a clear survival advantage. The tuned antennae, spectral filters and waveguides present in guard hair, all operating at a scale similar to the infrared wavelength, could be a rich source of bio-inspiration in the field of photonics⁠. The tools developed in this work may enable us to understand the other hair types and their evolution.

Potential counter-adaptations in predators of small rodents: If the infrared sensor interpretation of guard hair in small rodents is valid, there should be counter-adaptations in their common predators. A Leonardo Merlin camera was used to look for evidence of reduced infrared brightness or infrared concealment adaptations. Although only indicative at this stage there are some striking observations. Most warm-blooded animals appear very bright in thermal cameras but snakes, small cats and owls appear to be exceptions. Snakes in vegetation are virtually invisible in the thermal infrared, even during movement, so they are very effective ambush predators. The domestic cat, when hunting, has very weak infrared emission from the cold nose region and suppressed emission in general (Figure 7a). In the stalking pose, cats project the cold nose forward effectively compensating thermal emission from the eyes (which are in any case squinted).

Figure 7: (a) Is a typical thermal image of a domestic cat with a characteristic cold nose that is projected towards the prey during the stalking pose; (b) illustrates the cold centre of the facial disc of a barn owl, Tyto alba, and low emission from the feathered areas in general; (c) is a late frame from a video showing a barn owl diving onto a mouse with suppressed infrared emission in the direction of the prey.

“Fox (Vulpes Vulpes) Involvement Identified in a Series of Cat Carcass Mutilations”, Hull et al 2021

2021-hull.pdf: “Fox (Vulpes vulpes) involvement identified in a series of cat carcass mutilations”⁠, Kita D. Hull, Sonja Jeckel, Jonathan M. Williams, Sherryn A. Ciavaglia, Lucy M. I. Webster, Ella Fitzgerald et al (2021-12-06):

This study was designed to identify the cause of mutilation and death in 32 cats⁠, part of a larger cohort found dead in Greater London, the United Kingdom, between 2016 and 2018. At the time, discussion in the media led to concerns of a human serial cat killer (dubbed The Croydon Cat Killer) pursuing domestic cats, causing a state of disquietude. Given the link between animal abuse and domestic violence, human intervention had to be ruled out.

Using a combination of DNA testing, computed tomography imaging⁠, and postmortem examination, no evidence was found to support any human involvement. Instead, a large association between cat carcass mutilation and the presence of fox DNA was demonstrated (19⁄20). Gross examination identified shared characteristics including the pattern of mutilation, level of limb or vertebral disarticulation, wet fur, wound edges with shortened fur, and smooth or irregular contours, and marks in the skin, muscle, and bone consistent with damage from carnivore teeth. Together these findings supported the theory that the cause of mutilation was postmortem scavenging by red foxes (Vulpes vulpes).

The probable cause of death was established in 26⁄32 (81%) carcasses: 10 were predated, 8 died from cardiorespiratory failure, 6 from blunt force trauma, one from ethylene glycol toxicity, and another from liver failure. In 6 carcasses a cause of death was not established due to autolysis and/​or extensive mutilation.

In summary, this study highlights the value of a multidisciplinary approach to fully investigate cases of suspected human-inflicted mutilation of animals.

[Keywords: Felis catus, forensic pathology⁠, mutilation, postmortem examination, scavenging patterns, predation, veterinary forensics, DNA analysis, Vulpes vulpes]

…This raises the question regarding predatory behavior, and whether foxes have always preyed on cats or changes in population densities of cats and foxes in urban areas or food availability have led to predatory behavior. In our study, all those predated were kittens or juveniles, which suggests small size or “inexperience” may be predisposing factors, although one might equally consider older animals weakened by debilitating diseases to appear equally vulnerable.

…During the initial phases of the serial cat killer persona, there were certain features that raised particular concern for human involvement. One was the location of the mutilation, in that many of the carcasses had been “beheaded” or were missing tails. Our study confirmed that heads, necks, and tails were the most frequently mutilated body parts, but also detected forelimb mutilation at the scapula-body wall articulation, and less often complete carcass transection. These are similar to the scavenging patterns of foxes on lambs, where the nose, ears, tails, and heads are most often missing, but disarticulated limbs and transected spines are also detected. In over half of the cat carcasses predated or scavenged by coyotes, carcass transection was also identified, but individual missing heads, necks, tails, or forelimbs were not. These observations demonstrate clear differences in the mutilation pattern between the coyote and red fox when scavenging cat carcasses, but similarities in the scavenging patterns of the red fox on different but comparably sized species (ie. cats and lambs). Interestingly, when foxes scavenge larger carcasses such as deer they are seen to target extremities or the most decomposed areas in preference to the head or neck, and when cattle are targeted, lips, udders, or genitalia are removed first. A possible explanation for these variations in scavenging patterns between the small and larger carcasses is the increased strength required to dismember larger carcasses. Adult foxes are solitary scavengers and dismantle carcasses on their own, in contrast to dogs and wolves that operate in groups and can tear carcasses apart together with more combined force. Moreover, foxes are also reported to have relatively weak jaws, and thus may remove accessible soft tissues or disarticulate weaker joints that can be more easily gripped. In humans, joints that support more weight such as the knee or lumbar spine decompose more slowly and are more difficult to disarticulate than cervical vertebrae and the scapula, and studies have shown a clear link between the level of autolysis and disarticulation pattern from canine scavenging. This study proposes that the same happens with cat carcasses, as there was frequent disarticulation of cervical vertebrae and scapula, with no evidence of hind limb disarticulation at the hip or stifle joint. Given that most tail disarticulations occurred between Cd2 and Cd5, these joints may either provide good leverage and/​or be weaker and decompose more quickly.

“Toxoplasmosis: Recent Advances in Understanding the Link Between Infection and Host Behavior”, Johnson & Johnson 2020

2021-johnson.pdf: “Toxoplasmosis: Recent Advances in Understanding the Link Between Infection and Host Behavior”⁠, Stefanie K. Johnson, Pieter T. J. Johnson (2020-11-02; ):

Humans, wildlife, and domestic animals are intimately linked through shared infections. Many parasites and pathogens use multiple host species, either opportunistically or sequentially, such that managing disease risk frequently requires a broader understanding of the ecological community. The coccidian protozoan Toxoplasma gondii infects more than one hundred species of vertebrates, ranging from bats to beluga whales. In humans, acute toxoplasmosis can have serious health consequences for immunocompromised individuals. Even amongst asymptomatic patients, however, toxoplasmosis has been linked to a range of behavioral alterations and conditions, such as changes in risk tolerance, neuroticism, mental illness, suicide, and accident proneness. Whether such links are causal or simply correlational has been the subject of intense study and debate; from an evolutionary standpoint, selection may favor parasite-induced alterations in host behavior that increase the likelihood a host is consumed by the definitive host—in this case a domestic or wild felid. Here, we examine current evidence for parasite-induced manipulations of host behavior, in both humans and other animals. We critically evaluate proposed mechanisms through which infection might influence host behavior, which range from inflammation in the brain to changes in hormones or neurotransmitters. Considering estimates that T. gondii may infect up to 1⁄3rd of the global human population, we conclude by examining the implications of these changes for human behavior, individual fitness, and emergent cultural properties.

“The Relationship between Plant-eating and Hair Evacuation in Snow Leopards (Panthera Uncia)”, Yoshimura et al 2020

“The relationship between plant-eating and hair evacuation in snow leopards (Panthera uncia)”⁠, Hiroto Yoshimura, Huiyuan Qi, Dale M. Kikuchi, Yukiko Matsui, Kazuya Fukushima, Sai Kudo, Kazuyuki Ban et al (2020-07-10; backlinks; similar):

Although most felids have an exclusive carnivore diet, the presence of plant matter in scat has been reported among various species. This indicates that there may be an adaptive importance to the conservation of plant-eating behavior in felid evolution. Some studies have hypothesized that felids consume plants for self-medication or as a source of nutrition. In addition, it is thought that plant intake helps them to excrete hairballs, however, no scientific work has confirmed these effects. Thus, the objective of this study is to investigate the relationship between plant intake and hair evacuation in felid species. We selected snow leopards (Panthera uncia) as the study species because they have longer and denser hair than other felids. The behavior of 11 captive snow leopards was observed and scat samples from 8 of them and 2 other captive individuals were analyzed. Snow leopards evacuate hair possibly by vomiting and excreting in scats. The frequency of plant-eating and vomiting and the amount of hair and plant in scat were evaluated. We found that the frequency of vomiting was much lower than the frequency of plant-eating. In addition, there was no statistically-significant relationship between the amount of plant matter contained in scats and the amount of hair in scats. Contrary to the common assumption, our results indicate that plant intake has little effect on hair evacuation in felid species.

“Why Cats Love Earwax”, Branwen 2019

Earwax: “Why Cats Love Earwax”⁠, Gwern Branwen (2019-11-05; ⁠, ; backlinks; similar):

While petting cats⁠, I accidentally discovered cats are fascinated by the smell & taste of earwax⁠, particularly that of humans, and this interest can last indefinitely. Dogs & humans, for comparison, are not. A number of anecdotes have reported this over the years, but no formal research appears to have been done on this. What makes earwax attractive to cats? Pheromones? Some nutrient?

The best candidate to date is valeric acid⁠, which is present in both human earwax & the cat attractant plant Valerian⁠.

“The Use of Animal-borne Cameras to Video-track the Behaviour of Domestic Cats”, Huck & Watson 2019

2019-huck.pdf: “The use of animal-borne cameras to video-track the behaviour of domestic cats”⁠, Maren Huck, Samantha Watson (2019-08-01; backlinks):

  • Animal-born mini-cameras allow video-tracking of free-ranging domestic animals.
  • Video-tracking allows reliable behavioural data collection without observer effects.
  • A comprehensive cat ethogram is validated for cat-camera footage.
  • Video-tracking could be used for conservation and animal welfare studies.
  • Suggested applications include the study of predation behaviour of domestic cats.

Free roaming domestic animals can have a profound effect on wildlife. To better understand and mitigate any impact, it is important to understand the behaviour patterns of the domestic animals, and how other variables might influence their behaviour.

Direct observation is not always feasible and bears the potential risk of observer effects. The use of animal-borne small video-cameras provides the opportunity to study behaviour from the animal’s point of view. While video-tracking has been used previously to study specific aspects of the behaviour of a species, it has not been used so far to determine detailed time-budgets.

The aim of this study was to provide and validate an ethogram based on cat-camera footage collected from 16 cats (Felis catus). The methodology was validated comparing films recorded simultaneously, from both collar-mounted video recorders and hand-held video recorders. Additionally, the inter-observer reliability of scorers was measured. Continuous and instantaneous recording regimes were compared, and behavioural accumulation curves were evaluated to provide further technique recommendations for video-tracking cats.

Video-tracking allows scoring of behaviour as reliably as direct observation (linear mixed effects model: t < 0.001, p = 0.99; df = 14 in 7 cats; Cohen’s κ = 0.88). Furthermore, inter-observer reliability was high (Cohen’s κ = 0.72) and was not statistically-significantly different from 0.8 (one-sample t-test: t = 1.15. df = 5, p = 0.30), indicating that the method is not subject to bias in observers. Recommendations are given for the most efficient scoring protocol to reliably record feline behaviour.

While the validation was concerned with cat behaviour, the approach can be easily adapted for a variety of domestic species, as well as some captive animals. Video-tracking offers a new avenue to investigate both general time-budgets and more specific behaviours such as foraging or space use from the animal’s point of view and in its normal environment, without restrictions to movement. Insights gained through video-tracking will be relevant to various conservation and animal welfare issues.

“Optimizing Colour for Camouflage and Visibility Using Deep Learning: the Effects of the Environment and the Observer's Visual System”, Fennell et al 2019

“Optimizing colour for camouflage and visibility using deep learning: the effects of the environment and the observer's visual system”⁠, J. G. Fennell, L. Talas, R. J. Baddeley, I. C. Cuthill N. E. Scott-Samuel (2019-05-29; ; similar):

Avoiding detection can provide large survival advantages for prey, predators, or the military; conversely, maximizing visibility would be useful for signalling. One simple determinant of detectability is an animal’s colour relative to its environment. But identifying the optimal colour to minimize (or maximize) detectability in a given natural environment is complex, partly because of the nature of the perceptual space.

Here for the first time, using image processing techniques to embed targets into realistic environments together with psychophysics to estimate detectability and deep neural networks to interpolate between sampled colours, we propose a method to identify the optimal colour that either minimizes or maximizes visibility.

We apply our approach in 2 natural environments (temperate forest and semi-arid desert) and show how a comparatively small number of samples can be used to predict robustly the most and least effective colours for camouflage. To illustrate how our approach can be generalized to other non-human visual systems, we also identify the optimum colours for concealment and visibility when viewed by simulated red-green colour-blind dichromats⁠, typical for non-human mammals.

Contrasting the results from these visual systems sheds light on why some predators seem, at least to humans, to have colouring that would appear detrimental to ambush hunting. We found that for simulated dichromatic observers, colour strongly affected detection time for both environments. In contrast, trichromatic observers were more effective at breaking camouflage.

Figure 4: The effectiveness of tiger colouring in the dichromat context is striking. Image of a tiger (Panthera tigris) from the point of view of a simulated dichromat (a) and trichromat receiver (b). (Online version in color.)

“Chronic Lower Urinary Tract Signs in Cats”, DVM et al 2019

2019-westropp.pdf: “Chronic Lower Urinary Tract Signs in Cats”⁠, Jodi L. Westropp DVM, Mikel Delgado CAAB, C. A. Tony Buffington DVM (2019-01-01)

“Intestinal Delta-6-desaturase Activity Determines Host Range for Toxoplasma Sexual Reproduction”, Genova et al 2019

“Intestinal delta-6-desaturase activity determines host range for Toxoplasma sexual reproduction”⁠, Bruno Martorelli Di Genova, Sarah K. Wilson, J. P Dubey, Laura J. Knoll (2019; ):

Many eukaryotic microbes have complex life cycles that include both sexual and asexual phases with strict species specificity. Whereas the asexual cycle of the protistan parasite Toxoplasma gondii can occur in any warm-blooded mammal, the sexual cycle is restricted to the feline intestine. The molecular determinants that identify cats as the definitive host for T. gondii are unknown. Here, we defined the mechanism of species specificity for T. gondii sexual development and break the species barrier to allow the sexual cycle to occur in mice. We determined that T. gondii sexual development occurs when cultured feline intestinal epithelial cells are supplemented with linoleic acid. Felines are the only mammals that lack delta-6-desaturase activity in their intestines, which is required for linoleic acid metabolism, resulting in systemic excess of linoleic acid. We found that inhibition of murine delta-6-desaturase and supplementation of their diet with linoleic acid allowed T. gondii sexual development in mice. This mechanism of species specificity is the first defined for a parasite sexual cycle. This work highlights how host diet and metabolism shape coevolution with microbes. The key to unlocking the species boundaries for other eukaryotic microbes may also rely on the lipid composition of their environments as we see increasing evidence for the importance of host lipid metabolism during parasitic lifecycles. Pregnant women are advised against handling cat litter, as maternal infection with T. gondii can be transmitted to the fetus with potentially lethal outcomes. Knowing the molecular components that create a conducive environment for T. gondii sexual reproduction will allow for development of therapeutics that prevent shedding of T. gondii parasites. Finally, given the current reliance on companion animals to study T. gondii sexual development, this work will allow the T. gondii field to use of alternative models in future studies.

“On the Rheology of Cats”, Fardin 2014

2014-fardin.pdf: “On the rheology of cats”⁠, M. A. Fardin (2014-07-09; ⁠, )

“The “tomcat Compound” 3-mercapto-3-methylbutanol Occurs in the Urine of Free-ranging Leopards but Not in African Lions or Cheetahs”, Apps et al 2014

2014-apps.pdf: “The “tomcat compound” 3-mercapto-3-methylbutanol occurs in the urine of free-ranging leopards but not in African lions or cheetahs”⁠, Peter Apps, Lesego Mmualefe, Neil R. Jordan, Krystyna A. Golabek, J. Weldon McNutt (2014-04-01):

  • Unique study uses GC-MS to detect tomcat urine odour in wild leopard scent marks.
  • Wild leopards, but not lions or cheetahs have the tomcat odor compound in urine.
  • Urine odor results from wild big cats reconcile conflicting results from captive cats.

The felid-specific urinary odour compound 3-mercapto-3-methylbutanol and its precursors have been found in several felid species in captivity, but its presence in wild felids has not previously been investigated.

We analysed the naturally deposited scent marks from 3 species of wild, free-ranging big cats in Northern Botswana and found:

3-mercapto-3-methylbutanol in 4 samples of leopard urine (n = 13), but not in lion urine (n = 15) or cheetah urine (n = 6).

Individual variation in the presence of the tomcat compound in samples from big cats in the wild may reconcile conflicting results from captive cats.

[Keywords: Panthera pardus, Panthera leo, Acinonyx jubatus, Felis silvestris⁠, Cauxin⁠, Felinine]

“Do Cat Restrictions Lead to Increased Species Diversity or Abundance of Small and Medium-sized Mammals in Remnant Urban Bushland?”, Lilith et al 2010

2010-lilith.pdf: “Do Cat Restrictions Lead to Increased Species Diversity or Abundance of Small and Medium-sized Mammals in Remnant Urban Bushland?”⁠, Maggie Lilith, Michael Calver, Mark Garkaklis (2010; backlinks):

We took advantage of cat regulations enacted within differing subdivisions in the City of Armadale, Western Australia, to test the hypotheses that the species diversity (measured by the Shannon-Weiner index) and abundance of small and medium-sized mammals should be higher in native bushland within or adjacent to subdivisions where cats are restricted compared to similar areas where cats are not restricted.

There were three different regimes of cat regulation: no-cat zone (strict prohibition of cat ownership applying in one site), compulsory belling of cats and night curfew at one site, and unregulated zones (free-roaming cats applying at two sites). Both sets of cat regulations were in place for ~10 years prior to our survey.

We also measured structural and floristic features of the vegetation at each site that might influence the species diversity and abundance of small and medium-sized mammals independently or interactively with cat activity. No statistically-significant differences in species diversity were found across the sites and KTBA (known-to-be-alive) statistics for Brushtail Possums Trichosurus vulpecula and Southern Brown Bandicoots Isoodon obesulus, the two most abundant medium-sized mammals present, were similar across all sites. The smaller Mardo Antechinus flavipes, which could be regarded as the most susceptible to cat predation of all the native species trapped because of its size, was trapped mostly at an unregulated cat site. Total mammals trapped at the unregulated cat sites exceeded those caught at the two sites with restrictions, but these unregulated sites also had significantly denser vegetation and there was a borderline (p = 0.05) rank correlation between vegetation density and mammal captures across all sites.

It appears that pet cats are not the major influence on the species diversity or abundance of small and medium-sized mammals at these sites and that vegetation characteristics may be more important.

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