Establishing and Maintaining an Etruscan Shrew Colony

Abstract

The Etruscan shrew (Suncus etruscus) is one of the smallest mammals on earth and is used in many fields of research, including physiology, behavioral science and neuroscience. However, establishing and maintaining a breeding colony of this species in the laboratory can be challenging, as it requires specific husbandry conditions that greatly differ from those of more common laboratory species such as mice or rats. Over the past 15 y, we have successfully established a long-term thriving colony of 150 to 200 animals originating from 36 founders. The colony shows longer life expectancy and larger litter sizes than wild conspecifics. Breeding occurs year-round, independent of seasons, and a breeding pair can regularly produce 2 to 6 offspring with an average life expectancy of more than 3 y. The shrews are housed in glass or plastic enclosures on a specific soil-sand-mixture bedding and are provided with hideouts and nesting material consisting of moss, wood, or bark. Due to their high basal metabolic rate, the shrews require food intake greater than their body weight per day, can hunt arthropods as large as themselves, and cannot survive more than a few hours without food. Live feed such as crickets or mealworms is crucial and must be provided daily or, at the very least, every 2 d. Although our husbandry practices have constantly been adapted and refined, shrew husbandry remains challenging, and great care is necessary to meet the specific needs of this species. Here, we describe the establishment of a long-term stable colony of Etruscan shrews in a research animal facility and the specific husbandry requirements for animal wellbeing.

Figure 1.

Images of Suncus etruscus. A) Female Etruscan shrew in one of our housing devices. Please note the use of bark enrichment for hiding. B) Gender determination of a female Etruscan shrew. Please note the flat anus close to the tail base (white arrow) and the 3 teats on each side of the abdomen between the hind leg and anus (white asterisks). Scale bar 1 cm. C and E) Gender determination of a male Etruscan shrew. C) A male Etruscan shrew can be distinguished by the slightly visible internal testicles posterior of the anus (black arrow). Scale bar 1 cm. D) Typical size of an Etruscan shrew. Scale bar 6,5 cm. E) Especially notable are the male-specific lateral glands (white asterisk) in the region of the lateral thorax, the greasy secretion of which is responsible for the distinct smell of male Etruscan shrews. Scale bar 1 cm.

Figure 2.

A) Plastic container with removable and foldable but shrew-proof lid with 2 ventilation insets. The lid needs to tightly seal the container since shrews are very good jumpers and climbers and may squeeze through gaps only a few millimeters in width and thus may easily escape, which would quickly lead to death by starvation and dehydration. B) The container for general husbandry (not breeding) with bedding, enrichments and 2 separate water sources – bowl and bottle. It is important to create many retreats for the animals. Scale bars, 5 cm. C) Open container. The lid is folded back in its centerline and shows the stainless-steel mesh insets for ventilation (mesh size between 2 and 3 mm). Of note, the mesh is soldered into the plastic to prevent escape or injuries, for example during handling or cleaning.

Figure 3.

Various enrichment possibilities in a glass terrarium, such as A) wood, bark, egg packaging, clay pots beside water bottle and dish and B) pine cones, moss, and coconut shells. Scale bar, 5 cm.

Figure 4.

Labyrinth stone with young (A) in nest and 2 shrews (B). The stone is made of plaster and measures 30 · 25 · 6 cm similar as described by others. Passages and chambers were manually scratched into the stone. Scale bar, 3 cm.

Figure 5.

Example category of a score sheet: feeding behavior. Please note: when using a scoring scheme, especially with a numeric addition as above, please be aware to group parameters or symptoms to one specific corresponding behavioral, appearance, or organ complex. For example, excretions in the nose area may be grouped to outward appearance or to symptoms of the respiratory tract. If this specific criterion is, however, stated twice, that is once each in both complexes, it would be scored twice, leading to a higher score than actually present, which should be avoided in order not to falsify the scoring. Categories of 0 delineate the normal behavior of the shrew. This may be omitted. However, particularly concerning exotic species, this may facilitate the aim of the scoring sheet, that is every observer scoring equally.

Figure 6.

Comparison of the number of progeny per breeding pair (n = 217) in selected consecutive litters of the same breeding pair. The graph illustrates a distinct decline in the number of progeny per litter with increasing numbers of litters per breeding pair, each from litter one to litter 5 and litter 5 to litter 10. Only one 15^th litter was recorded with a single pup during the entire period of investigation. The most frequent are 3 and 4 offspring (58 and 48%) born in the first litter.