Porous structures inspired by porcupine quill: multiscale design optimization approach.

This paper presents a novel approach for designing a freeform bending-resistant structure from the combination of explicit discrete component-based topology optimization (TO) and the porcupine quill-inspired features. To embed the porcupine quill's features into the TO formulations, the method involves constructing discrete components at various scales to imitate features including solid shell, stochastically distributed pores, and graded stiffeners. The components are iteratively updated, and the optimization process allows for the grading of quill-inspired features while achieving optimal structural compliance under bending loads. The proposed approach is demonstrated to be effective through the resolution of Messershmitt-Bolkow-Blohm (MBB) beam designs, parameterized studies of geometric parameters, and numerical validation of long-span and short-span quill-inspired beam designs. By examining the von Mises stress distribution, the study highlights the mitigation of material yielding at the shell region brought by the geometric features of porcupine quills, leading to the potential theory support for the bending resistance. The optimized MBB beams are manufactured using the material extrusion technique, and three-point bending tests are conducted to explore the failure mitigation capability of the quill-inspired beam under large deformation. Consequently, the study concludes that the proposed quill-inspired component-based TO approach can design a structure with excellent bending resistance according to the improved energy absorption as well as increased deformation after reaching 75% peak load.

Preliminary investigation on enzymatic activity in saliva of Hystrix cristata L., 1758.

Mammal's saliva contains a variety of electrolytes and proteins. They carry out an important role in the digestion process, in the antibacterial and antiviral activity, in lubrication and maintenance of oral general health status. It may also contain several enzymes according to dietary habits and general wellness. Sialochemistry is a valid alternative to the haematochemical analysis for the evaluation of animal health and nutritional status. At present, very little knowledge is available on health status and pathology of crested porcupine (Hystrix cristata) and no data are yet available on salivary enzymes. Between 2018 and 2020, a preliminary investigation of enzymatic activity on saliva samples was carried out from captured porcupines. In crested porcupine saliva, enzymatic activity of trypsin, chymotrypsin, N-Aminopeptidase, amylase, lignin peroxidise, cellulase and chitinase were recorded. Superoxide dismutase, catalase, glutathione S-transferase and alkaline phosphatase activity was also detected. The superoxide dismutase activity resulted higher (3.13 SD 3.58 U/mg proteins) than those of catalase (130.80 SD 110.65 mU/mg proteins) and glutathione S-transferase (20.21 SD 16.62 mM/mg proteins). Alkaline phosphatase activity resulted lower (5.91 SD 6.12 mU/mg proteins) than acidic phosphatase (19.00 SD 16.16 U/mg proteins) with the highest values of saliva alkaline phosphatases recorded in young individuals. These preliminary data bring new knowledge on crested porcupine saliva enzymes and may provide a useful tool for further investigation on the adaptive response of crested porcupine to different environmental condition and diet. Additional investigation concerning a possible alternative use of saliva enzymes as indicator of health and nutritional status of this rodent are desirable.

Reproductive behaviour in free-ranging crested porcupine Hystrix cristata L., 1758.

Previous data on crested porcupine reproduction biology were mostly collected in captivity or semi-captivity due to its elusive, burrowing and mainly nocturnal habits. Between 2017 and 2019 the reproductive behaviour (i.e., intrapair mounting and copulation, birth and parental care) of free-ranging crested porcupine was documented and described. Nightly rhythms of single and multiple mounting occurred throughout the year while only two copulation events were recorded. Three months after both copulation events, the birth of porcupettes (porcupine < 5 kg) was recorded. A stochastic phase characterized by an articulate courtship with distinct behavioural patterns always preceded each mounting event. After the stochastic phase, the presenting of the female evoked by Nose-Quill contact behaviour, occurred in 83.8% (n = 182) of mounting events, while in 16.1% (n = 35) a spontaneous presenting of the female occurred. The average duration of copulation lasted 24 s (SD = 7 s) with 17 thrusting (SD = 5.5 thrusting). Births of porcupettes occurred throughout the year from 1 to 3 times per pair per year and the litter size observed ranged from 1 to 2 porcupettes. The first emerging of porcupettes from burrow occurred at 10-15 days after birth. Parents and sub-adults of the family actively perform parental care and the permanence of sub-adults within the family (i.e., from birth to dispersal) resulted to be at least 1 year. This investigation provides new useful insights on porcupine reproductive behaviour in the wild. Such new knowledge may be useful to the management of porcupines in wild, semiwild and captive condition as well as to delineate the key habitat desiderata of this rodent.

Evidence of scavenging behaviour in crested porcupine.

The vegetarian diet of many herbivorous mammals is supplemented with proteins of animal origin, especially in young individuals and in breeding females, to provide key proteins necessary for both growth and breeding. Among porcupine species, only the Cape porcupine (Hystrix africaeaustralis) has been observed to consume carrion flesh. From June to August 2019, a pigeon carcass was placed together with corn in 7 study settlements and near 2 monitored capture-traps, in order to assess the carrion flesh feeding habits of the crested porcupine (Hystrix cristata). Scavenging behaviour was recorded on four occasions. All the recorded individuals were adults and at least one was female. This demonstrates that the crested porcupine occasionally does eat flesh. Such evidence raises important questions concerning the relationship between feeding habits and the physiological needs of this herbivorous rodent.

Diurnal motor activity and "sunbathing" behaviour in crested porcupine (Hystrix cristata L., 1758).

The crested porcupine is a mainly nocturnal mammal that shows both moonlight avoidance and some diurnal motor activity, the latter as an extension of its night-time foraging behaviour. Furthermore, a peculiar daytime behaviour, described as "sunbathing", was reported as episodic in H. africaeaustralis. Between 2016 and 2019 a camera-trapping monitoring was performed within 10 porcupine settlements in order to detect the diurnal motor activity and to verify and describe the sunbathing behaviour in crested porcupine. Out of 1,003 trap days, a total of 148 events of diurnal motor activity were recorded. The diurnal motor activity occurred throughout the year mainly between December and June from 15:00 to 16:00, with no statistical difference between cubs, youngsters and adults. The sunbathing behaviour was detected for a total of 36 episodes recorded. Sunbathing was performed mainly by cubs. The sunbathing behaviour occurred only between April and June during the hottest hours of the day (11:00 to 12:00). Diurnal motor activity and sunbathing behaviour of porcupine are discussed in relation to food availability and porcupine physiology.

An immunohistochemical study on testicular steroidogenesis in the Sunda porcupine (Hystrix javanica).

In the testes of the Sunda porcupine (Hystrix javanica), the expression of the steroidogenic acute regulatory protein (StAR) and steroidogenic enzymes, such as cytochrome P450 side chain cleavage (P450scc), 3ß-hydroxysteroid dehydrogenase (3ß-HSD), cytochrome P450 17α-hydroxylase (P450c17) and cytochrome P450 aromatase (P450arom), was immunohistochemically examined to clarify the location of steroidogenesis. In this study, complete spermatogenesis (spermiogenesis) was observed in the testes of the examined Sunda porcupine, and spermatozoa of the Sunda porcupine had a spatulate sperm head unlike that of rats and mice which has an apical hook. On immunostaining of StAR, P450scc, 3ß-HSD, P450c17 and P450arom, immunoreactivity for all proteins was only detected in the Leydig cells and not observed within the seminiferous tubules, suggesting that the Leydig cells can synthesize both androgen and estrogen from cholesterol in the Sunda porcupine testes.

Crested porcupines (Hystrix cristata): mycophagist spore dispersers of the ectomycorrhizal truffle Tuber aestivum.

Truffles, as hypogeous, ectomycorrhizal fungi, have no means to actively discharge spores into the environment and thus depend on mycophagists for spore dispersal. After consumption of fruiting bodies by animals and passage through the digestive tract, the spores are released in faecal pellets. Recently, in the Abruzzo region (Italy), Hystrix cristata has been spotted inside private truffières, but its role in spore dispersal has never been investigated. Here, we report our research on the occurrence of Tuber aestivum spores in porcupine's faecal contents in a truffière in L'Aquila, Italy, where a H. cristata specimen was photographed. The spores were isolated from faeces by using a suspension of 0.7 M ZnSO4. We also verified degradation and disfiguration of the digested spores' reticular ornamentation compared to that of fresh spores from ascomata collected inside the truffière, through measurements performed by scanning electron microscopy. A few truffle spores had germinated within the faeces.

Undermining subsistence: Barren-ground caribou in a "tragedy of open access".

Sustaining arctic/subarctic ecosystems and the livelihoods of northern Indigenous peoples is an immense challenge amid increasing resource development. The paper describes a "tragedy of open access" occurring in Canada's north as governments open up new areas of sensitive barren-ground caribou habitat to mineral resource development. Once numbering in the millions, barren-ground caribou populations (Rangifer tarandus groenlandicus/Rangifer tarandus granti) have declined over 70% in northern Canada over the last two decades in a cycle well understood by northern Indigenous peoples and scientists. However, as some herds reach critically low population levels, the impacts of human disturbance have become a major focus of debate in the north and elsewhere. A growing body of science and traditional knowledge research points to the adverse impacts of resource development; however, management efforts have been almost exclusively focused on controlling the subsistence harvest of northern Indigenous peoples. These efforts to control Indigenous harvesting parallel management practices during previous periods of caribou population decline (for example, 1950s) during which time governments also lacked evidence and appeared motivated by other values and interests in northern lands and resources. As mineral resource development advances in northern Canada and elsewhere, addressing this "science-policy gap" problem is critical to the sustainability of both caribou and people.

Population dynamics of a northern-adapted mammal: disentangling the influence of predation and climate change.

Community structure and interspecific interactions are particularly vulnerable to rapidly changing climatic regimes. Recent changes in both climate and vertebrate community assemblages have created a unique opportunity to examine the impacts of two dynamic forces on population regulation. We examined the effects of warming winter conditions and the reestablishment of a previously extirpated predator, the fisher (Martes pennanti), on regulatory mechanisms in a northern-adapted mammal, the porcupine (Erethizon dorsatum), along their southern range boundary. Using a long-term (17-year) capture-recapture data set, we (1) quantified the impacts of climate change and increased fisher predation on the survival of adult porcupines at their regional southern terminus, (2) assessed recruitment (via both adult fecundity and juvenile survival) of porcupines, and (3) modeled the relative importance of predation and winter conditions on the demography and population growth rate (λ). Severe winters and abundant predators interacted synergistically to reduce adult survivorship by as much as 44%, while expanding predator populations led to near reproductive failure among porcupines. Increasing predatory pressure, disruptions in this community module, and more frequent extreme winter weather events led to predicted extirpation within 50 years, whereas in the absence of predators, the population was viable. Our results provide a mechanistic understanding behind distributional shifts resulting from climate change and may be broadly relevant for predicting future distributional shifts in other northern-adapted mammalian species.

Causes and consequences of change rates in the habitat of the threatened tropical porcupine, Sphiggurus mexicanus (Rodentia: Erethizontidae) in Oaxaca, Mexico: implications for its conservation / Causas y consecuencias de las tasas de cambio en el hábitat del puerco espín tropical amenazado, Sphiggurus mexicanus (Rodentia: Erethizontidae), en Oaxaca, México: implicaciones para su conservación

Land use changes by human activities have been the main causes of habitats and wildlife population degradation. In the Tehuantepec Isthmus in Oaxaca, the tropical habitat of the porcupine Sphiggurus mexicanus has been subject to vegetation and land use changes, causing its reduction and fragmentation. In this study, we estimated vegetation cover and land use (δn) change rates and assessed habitat availability and potential corridors for possible porcupine movements to avoid its isolation. In the study area, the type of vegetation with the most change rate value was the savanna (δn=-2.9), transformed into induced grasslands. Additionally, we have observed the porcupine (since 2011) in semi-deciduous (δn=-0.87) and tropical dry (δn=-0.89) forests that have been transformed in temporal agriculture and mesquite and induced grasslands. The vegetation inhabited by the porcupine resulted in recording a total of 64 plant species (44 trees, nine vines, seven herbs, four shrubs), of which the vine Bunchosia lanceolata showed the highest importance value (41.85) followed by the trees Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), and Enterolobium cyclocarpum (17.02). The habitat evaluation and potential corridor analysis showed that only 1 501.93ha could be considered as suitable habitats with optimum structural conditions (coverage, surface, and distances to transformed areas) to maintain viable populations of S. mexicanus, and 293.6ha as corridors. An increasing destruction of the porcupines’ habitat has been observed in the study area due to excessive logging, and actions for this species and its habitat conservation and management have to be taken urgently. Rev. Biol. Trop. 62 (4): 1481-1494. Epub 2014 December 01.

Los cambios de uso del suelo por actividades humanas, han sido de las principales causas de la degradación, reducción y fragmentación de los hábitats y poblaciones de fauna silvestre. En el Istmo de Tehuantepec, Oaxaca, el hábitat del puercoespín tropical Sphiggurus mexicanus, se encuentra sometido a cambios de cobertura vegetal y uso del suelo, que están causando la reducción y fragmentación de su hábitat. Debido a ello, estimamos las tasas de cambio de la cobertura vegetal y uso del suelo (δn), y evaluamos la disponibilidad del hábitat y de corredores vegetales potenciales para los posibles movimientos del puercoespín tropical y evitar su aislamiento. En el área de estudio el tipo de vegetación con mayor valor de tasa de cambio fue la sabana (δn=-2.9), transformado en pastizal inducido. Adicionalmente, observamos puercoespínes (desde 2011) en selva mediana subperennifolia (δn=-0.87) y selva baja caducifolia (δn=-0.89), los cuales han sido transformados en áreas de cultivo, selva baja espinosa y pastizal inducido. Caracterizamos la vegetación del hábitat del puercoespín, registrando un total de 64 especies vegetales (44 árboles, nueve bejucos, siete hierbas y cuatro arbustos), de los cuales, el bejuco Bunchosia lanceolata, presentó los valores más altos de importancia (41.85), seguidos por los árboles Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), y Enterolobium cyclocarpum (17.02). El análisis de evaluación de hábitat y corredores potenciales mostró que solo 1 501.93ha pueden considerarse como hábitats adecuados con condiciones estructurales (de cobertura, superficie y distancias a áreas transformadas) para mantener poblaciones viables de S. mexicanus; y 293.6ha como corredores. La destrucción del hábitat del puerco espín en el área de estudio está incrementándose por la tala excesiva, por lo tanto, es prioritario emprender acciones para la conservación y manejo del taxón y su hábitat.

Patterns of spatial overlap in a monogamous large rodent, the crested porcupine.

The crested porcupine Hystrix cristata is a large rodent which pairs for life. We studied the space use of 17 female and 9 male radio-tracked porcupines in an evergreen coastal woodland ("macchia", EW) and in an agricultural estate (AE), with special reference to the use of cultivations. Home range sizes of male porcupines (4.72-323.40) ranged around 114ha (median) during the warm period (April-September) and 162ha during the cold one (October-March). Home ranges of females (2.48-323.40) were c. 91ha during the warm period and c. 143ha during the cold one. Habitat composition and selection changed from the cold to the warm months, with porcupines being present in agricultural areas especially in the latter. Home range overlap between members of the same pair varied from 57% to 97% (median, 75%). Habitat selection was analyzed at the second (within study area) and at the third (within home range) order of selection. Within study areas, porcupines avoided cultivations and selected habitats with dense vegetation, providing cover and food. Within home ranges, in the warm period, porcupines selected agricultural areas in EW, where this habitat represented a minor portion of the study site. In that season, the Mediterranean "macchia" is a poor source of food, forcing porcupines to travel long distances to reach feeding sites. No significant difference of habitat selection within home ranges was detected between members of the same pair. Cultivations may play a key-role for porcupine survival, especially in poor habitats, as they provide abundant food resources in the warm period.

Causes and consequences of change rates in the habitat of the threatened tropical porcupine, Sphiggurus mexicanus (Rodentia: Erethizontidae) in Oaxaca, Mexico: implications for its conservation.

Land use changes by human activities have been the main causes of habitats and wildlife population degradation. In the Tehuantepec Isthmus in Oaxaca, the tropical habitat of the porcupine Sphiggurus mexicanus has been subject to vegetation and land use changes, causing its reduction and fragmentation. In this study, we estimated vegetation cover and land use (δn) change rates and assessed habitat availability and potential cor- ridors for possible porcupine movements to avoid its isolation. In the study area, the type of vegetation with the most change rate value was the savanna (δn = -2.9), transformed into induced grasslands. Additionally, we have observed the porcupine (since 2011) in semi-deciduous (δn = -0.87) and tropical dry (δn = -0.89) forests that have been transformed in temporal agriculture and mesquite and induced grasslands. The vegetation inhabited by the porcupine resulted in recording a total of 64 plant species (44 trees, nine vines, seven herbs, four shrubs), of which the vine Bunchosia lanceolata showed the highest importance value (41.85) followed by the trees Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), and Enterolobium cyclocarpum (17.02). The habitat evaluation and potential corridor analysis showed that only 1 501.93ha could be considered as suitable habitats with optimum structural conditions (coverage, surface, and distances to transformed areas) to maintain viable populations of S. mexicanus, and 293.6 ha as corridors. An increasing destruction of the porcupines' habitat has been observed in the study area due to excessive logging, and actions for this species and its habitat conserva- tion and management have to be taken urgently.

Field evaluation of some bait additives against Indian crested porcupine (Hystrix indica) (Rodentia: Hystricidae).

This research study evaluated the effect of different additives on the bait consumption by Indian crested porcupine, a serious forest and agricultural pest, under field conditions. Different additives (saccharin, common salt, bone meal, fish meal, peanut butter, egg yolk, egg shell powder, yeast powder, mineral oil and coconut oil) at 2 and 5% each were tested for their relative preference, using groundnut-maize (1:1) as basic bait. All the additives were tested under a no-choice test pattern. For control tests, no additive was mixed with the basic bait. Saccharin at 5% concentration significantly enhanced the consumption of bait over the basic bait, while 2% saccharin supplemented bait resulted in a non-significant bait consumption. All other additives did not enhance the consumption of the bait material; rather, these worked as repellents. However, the repellency was lowest with the common salt, followed by egg yolk, egg shell powder, bone meal, peanut butter, mineral oil, fish meal and yeast powder, while coconut remained the most repellent compound. The present study suggested that groundnut-maize (1:1) supplemented with 5% saccharin was the preferred bait combination, and can be used with different rodenticides for the management of Indian crested porcupine.

Habitat richness affects home range size in a monogamous large rodent.

In monogamous species, after pair formation, the main reason for ranging movements is not searching for a mate, but for other important resources e.g. food. We monitored a total of 20 radio-tagged adult, paired crested porcupines in four areas of different habitat richness. No sexual size dimorphism was assessed. Body mass and habitat richness showed collinearity. For both sexes, home range size was correlated to habitat richness, with a significant inverse exponential regression. Opposite to natural foragers, living in poor habitats, crop foragers had smaller home ranges, with their dens significantly closer to cultivations. Both availability of food resources and den sites are key variables to determine home range size.

A minimally invasive method for gender determination in the prehensile-tailed porcupine (Coendou prehensilis).

Prehensile-tailed porcupines (Coendou prehensilis), like other rodents, lack external sexual traits, making it difficult to non-invasively determine their gender. By exploiting genetic differences between the X and the Y chromosome, we developed a simple genetic test to determine the gender of Coendous from shed quills. We Sanger sequenced a short portion (195 bp) of the zinc finger protein gene of known male (XY) Coendous to identify positions that are polymorphic between the X and Y chromosomes at this locus. By directly sequencing this fragment, we were able to correctly determine (confirmed via anatomical sexing) the gender of male and female Coendous by the presences or absence of polymorphisms in the resulting chromatograms. This assay is simple, quick and is applicable to other porcupine species.

Winter as a nutritional bottleneck for North American porcupines (Erethizon dorsatum).

North American porcupines are distributed across a wide variety of habitats where they consume many different species of plants. Winter is a nutritional bottleneck for northern populations, because porcupines remain active when environmental demands are high and food quality is low. We used captive porcupines to examine physiological responses to low-quality diets at high energy demands during winter at ambient temperatures as low as -39 degrees C. We did not observe an endogenous pattern of body mass gain or loss when porcupines were fed a low nitrogen diet (1.1% dry matter) ad libitum through winter. Dry matter intake declined from 43.6 to 14.6 g kg(-0.75) d(-1) even though ambient temperatures declined from -3 to -30 degrees C, which indicates a seasonal decrease in metabolic rate. Porcupines consuming white spruce needles maintained digestive efficiency for energy (61%) and neutral detergent fiber (NDF) (50%). However, low requirements for energy (398 kJ kg(-0.75) d(-1)) and nitrogen (209 mg kg(-0.75) d(-1)) minimized the loss of body mass when intakes were low and plant toxins increased urinary losses of energy and nitrogen. Porcupines were also able to tolerate low intakes of sodium, even when dietary potassium loads were high. Porcupines use a flexible strategy to survive winter: low requirements are combined with a high tolerance for dietary imbalances that minimize the use of body stores when demands exceed supply. However, body stores are rapidly restored when conditions allow. Porcupines posses many physiological abilities similar to specialist herbivores, but retain the ability of a generalist to survive extreme conditions by using a variety of foods.

Behavioral archives link the chemistry and clonal structure of trembling aspen to the food choice of North American porcupine.

Understanding the links among plant genotype, plant chemistry, and food selection by vertebrate herbivores is critical to assess the role of herbivores in the evolution of plant secondary chemistry. Some specialized vertebrate herbivores have been shown to select plants differentially according to plant genotype, but examples from generalists, which constitute the vast majority of vertebrate herbivores, are few, especially in natural conditions. We examined the relationship between the North American porcupine (Erethizon dorsatum), a generalist mammalian herbivore, and clonal trembling aspen (Populus tremuloides), a preferred food source of porcupines. We determined preference for certain aspen trees through visual examination of porcupine climbing scars left on tree bark, and through a controlled feeding experiment. We used genetic and biochemical analyses to link the behavioral archives (climbing scars) left by porcupines on aspen trunks to the clonal structure and chemical composition of trees. We show that two phenolic glycosides (tremulacin and salicortin), which are under a high degree of genetic control and thus vary in concentration across clones, are the chemical variables that most influence (deter) feeding choices by porcupines. Using behavioral archives left by a wild herbivore on a natural stand of plants thus allowed us to demonstrate that a generalist vertebrate herbivore can choose plants according to their clonal structure and genetically based chemical composition. Our results contribute to extending previous findings obtained with generalist herbivores studied in controlled conditions, and with specialist herbivores studied in the field.

On the Indian crested porcupine, Hystrix indica (Kerr, 1792) in Turkey (Mammalia: Rodentia).

This study presents some data about ecological, biological and taxonomical characteristics of Hystrix indica (Kerr, 1792) from Turkey. For this purpose characteristics of burrow, skull, tooth and measurements of external and cranial characters of two female H. indica from Turkey were investigated. It was concluded that our specimens are between the Middle East and Indian sub-region specimens in terms of morphometrical. It was also determined that there were roots in stomach contents of specimens.

Functional anatomy of the limbs of erethizontidae (Rodentia, Caviomorpha): Indicators of locomotor behavior in Miocene porcupines.

Functional analysis of the limb bones of the erethizontid Steiromys duplicatus, one of the most abundant Miocene porcupines from Patagonia, provides evidence to infer their locomotor behavior. Remains of the giant Neosteiromys pattoni (Late Miocene of Northeast Argentina) are also analyzed. Osteological and myological features of extant porcupines were evaluated and used as a model to interpret the functional significance of Miocene species' limbs. Several features in erethizontids are compatible with the ability to climb: the low humeral tuberosities indicate a mobile gleno-humeral joint; the prominent and distally extended deltopectoral crest indicates a powerful pectoral muscle, which is particularly active when climbing; the humero-ulnar and humero-radial joints are indicative of pronation-supination movements; the well-developed lateral epicondylar ridge and the medially protruding entepicondyle are in agreement with an important development of the brachioradialis, supinator, flexor digitorum profundus, and pronator teres muscles, acting in climbing and grasping functions; the mechanical advantage of the biceps brachii would be emphasized because of its distal attachment on the bicipital tuberosity. As with extant porcupines, in Miocene species, the large femoral head would have permitted a broad range of abduction of the femur, and the medially protruding lesser trochanter would have emphasized the abduction and outward rotation of the femur by the action of the ilio-psoas complex. In S. duplicatus, the shape of the hip, knee, and cruro-astragalar, calcaneo-astragalar, and astragalo-navicular joints would have allowed lateral and rotational movements, although probably to a lesser degree than in extant porcupines. Foot features of S. duplicatus (e.g., great medial sesamoid bone, medial astragalar head, complete hallux) indicate that this species would have had grasping ability, but would not have achieved the high degree of specialization of Coendou. Steiromys duplicatus would have been a semiarboreal dweller, resembling Erethizon dorsatum.

Conspicuous and aposematic spines in the animal kingdom.

Spines serve as a common physical defence mechanism in both the plant and animal kingdoms. Here we argue that as in plants, defensive animal spines are often conspicuous (shape and colour) and should be considered aposematic. Conspicuous spines may evolve as signals or serve as a cue for potential predators. Spine conspicuousness in animals has evolved independently across and within phyla occupying aquatic and terrestrial ecosystems, indicating that this convergent phenomenon is highly adaptive. Still, many spines are cryptic, suggesting that conspicuity is not simply constrained by developmental factors such as differences in the chemical composition of the integument. Aposematism does not preclude the signalling role of conspicuous spines in the sexual arena.