Introduction
Understanding the dietary habits of a species is crucial for deciphering its ecological role, especially when dealing with species considered as pests. Analyzing a pest species' diet allows us to evaluate its potential effects on other components of the ecosystem. This article delves into the diet and nutritional aspects of Atelerix frontalis, commonly known as the Southern African hedgehog, drawing upon existing research and observations. Information on a species’ diet is vital in understanding its ecological relationships, particularly for a pest species, where it also allows an assessment of potential impacts on other ecosystem components.
General Dietary Habits of Hedgehogs
Hedgehogs, belonging to the family Erinaceidae, exhibit flexible and opportunistic feeding behaviors. They inhabit diverse environments, ranging from deserts to temperate forests, which influences their dietary choices. Their natural diets encompass invertebrate and vertebrate prey, carrion, and plant material. European hedgehogs Erinaceus europaeus are native to much of western Europe and were introduced to New Zealand in the late nineteenth century, where they are now widespread and occupy many habitat types. Recent evidence has implicated hedgehogs as significant predators of endemic wildlife in island ecosystems into which they have been introduced, including New Zealand.
Nutritional Requirements
Despite their widespread distribution and popularity as pets, specific nutritional requirements of hedgehogs remain largely unknown. Hedgehogs possess the enzymatic ability to digest chitin, a component of insect exoskeletons, using it as a dietary fiber source. However, their ability to digest cellulose efficiently appears limited.
Southern African Hedgehog: An Overview
Southern African hedgehogs are small mammals found throughout southern Africa, specifically in Botswana, Malawi, Namibia, South Africa, and Zimbabwe. There are two specific ranges of this hedgehog, a western range including Angola and Namibia and an eastern range, including South Africa, Mozambique, Lesotho, Zimbabwe, and Botswana. These hedgehogs are dark brown with spines typically white at the base and dark brown at the tip. They prefer grass and Bushveld environments that aren't overly damp and have ample leaf cover. They are solitary animals, maintaining a home range of 200-300 meters and sleeping in different locations daily.
Dietary Analysis in a New Zealand Dryland Habitat
A study was conducted in a 60-ha strip of dryland habitat in South Island, New Zealand, to analyze the diet of hedgehogs. The climate in the area is semi-arid continental and is characterized by relatively extreme seasonal and diurnal temperature ranges and low and unpredictable rainfall (annual mean, 360 mm). Prey availability was estimated using pitfall traps, and hedgehog diets were investigated through fecal analysis. This method is commonly used in the study of insectivore diets, including those of hedgehogs. Diets were analyzed at both individual and population level. For population-scale analysis, droppings were collected opportunistically by observation whilst traversing the study site on foot from early February to mid-April 2003.
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Methods of Studying Hedgehog Diets
Most studies of hedgehog diet, in both New Zealand and Europe, have described consumption by hedgehogs in terms of the frequency of occurrence of a particular food type. This method is relatively robust for large sample sizes and enables comparisons between studies to be made, but the equal weight assigned to single and multiple items of different food types in a single sample can lead to biassed estimates of the relative importance of different foods to the consumer. Accordingly, frequency-of-occurrence data alone can allow only limited inference as to whether foods are actively selected or avoided. To study the diets of individual hedgehogs, it was necessary to associate droppings with the animal producing them. Eleven animals were live-trapped in early February 2003. Captured hedgehogs were weighed and sexed, and a two-stage radio transmitter was attached by glueing it to a trimmed section of dorsal spines.
Prey Availability Assessment
Availability of hedgehog prey was estimated using 120 pitfall traps distributed randomly throughout the study site. Each trap consisted of a 535-ml plastic food container (124 mm deep by 98 mm diameter) sunk into the ground so that the rim was flush with the ground surface. A small drainage hole in the bottom of each trap prevented accidental drowning of any captured McCann’s skinks or invertebrates in the event of rain. Traps were protected with a raised wooden cover and left open for six nights in late March 2003.
Fecal Analysis
Diet composition was investigated by analysis of hedgehog droppings. Overall, 137 droppings were collected, 77 of which were from known individuals and 60 from opportunistic collection. Prior to analysis, they were oven-dried to constant mass for 72 h at 50°C and weighed. After they were washed through a fine-meshed sieve, prey remains were viewed through a binocular dissecting microscope and identified using a variety of diagnostic structures (heads, elytra, legs, antennae, forceps). Invertebrate remains were generally identified to order, except for Coleoptera, which were identified to family and occasionally to species, using the reference collection and another collection of preserved local invertebrate fauna. Vertebrate remains were readily identifiable, and each sample was scanned visually for the presence of earthworm chaetae.
Results of the Diet Analysis
Population-Level Diet
The food types most commonly eaten by hedgehogs were beetles (Coleoptera), found in 94% of droppings, and earwigs (Dermaptera), in 92% of droppings. Remains of the locally restricted large sand scarab Pericoptus frontalis and rare Alexandra chafer Prodontia modesta were identified in 16% and 5% of droppings, respectively. Identifiable lizard remains (14% of samples) ranged from a few scales to whole feet and bone fragments. One dropping contained the remains of at least 10 separate McCann’s skink feet and another at least eight feet from the same species. Bird remains were found in 10% of droppings. Plant remains, generally of leaves and blades of grass, were seen in 49% of samples.
Individual Diets
Some foods contributed significantly more than others to individuals’ diets (Friedmann chi-square = 7.02, df = 11, p < 0.001), but use of these foods did not vary significantly between individuals (Friedmann chi-square = 4.69, df = 8, p = 0.79). In general, food use conformed to the pattern seen at the population scale with heavy dependence on beetles (21-54% of the dry faecal mass of each animal) and earwigs (13-39%). The degree of dietary overlap between individuals was generally high. Mean overlap (36 pairs) was 0.84 (0.01 SE).
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Discussion
General Diet Composition
In the New Zealand study, beetles were found in 94% of samples, a common finding in both European and some New Zealand studies. Earwigs occurred in large numbers in most droppings, many of which consisted of at least 80% earwig remains, with one sample containing nothing else. Very small quantities of spider remains were found in 25% of droppings. These were mostly nocturnally active wolf spiders. All identifiable Orthoptera remains were grasshoppers. The heavy consumption of beetles by hedgehogs may be of concern for the conservation values at our study site as two at-risk species were eaten.
Predation on Native Lizards
Predation by hedgehogs on native lizards may also be of concern to conservation managers. Lizard remains were found in one in seven droppings in this study. The presence of 10 McCann’s skink feet in one sample indicates that at least three skinks were eaten in a single feeding bout.
Opportunistic Feeding
Hedgehogs’ ability to take full advantage of temporarily abundant foods is exemplified by the occurrence of large numbers of molluscan eggs in faecal samples obtained over a relatively short and well-defined period. Similar behaviour has been described in both New Zealand and Europe where hedgehogs took advantage of temporarily abundant grass grubs, cockchafer beetles and aphid eggs.
Absence of Earthworms in Diet
Some studies have noted the importance of earthworms in hedgehog diets, but the New Zealand study found no evidence of earthworm chaetae to indicate consumption, nor were any earthworms seen when digging-in the 120 pitfall traps. The absence of earthworms was probably due to the very dry soil conditions at the time of the study. Earthworms require sufficient soil moisture to thrive, making them less accessible to hedgehogs in dry conditions.
Dietary Adaptations
Hedgehogs have several adaptations related to their diet. Their brachydont teeth, with large, forward-projecting incisors and flattened molars, are well-suited for grasping and crushing insects and other invertebrates. They also have a simple stomach and a vomiting reflex, which may help them to eliminate toxins or indigestible material from their diet.
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Hedgehogs as Pets: Nutritional Considerations
When kept as pets, hedgehogs require a balanced diet that meets their nutritional needs. A high-quality, commercial hedgehog food can form the basis of their diet, supplemented with small amounts of insects, cooked meat, and vegetables. It is important to avoid feeding them sugary or fatty foods, as these can lead to obesity and other health problems.