Slender shrews successfully bred in captivity

A research group including Assistant Professor Satoshi Ohdachi of the Institute of Low Temperature Science at Hokkaido University, in collaboration with Tokai University, and Sapporo Maruyama Zoo, has successfully bred slender shrews (Sorex gracillimus) in captivity. This is the first time that mating behavior, gestation period, lactation and weaning processes, and neonatal development have been clarified. The results are expected to contribute to the conservation of endangered species and foundational biological research. The findings were published in the journal Mammal Study on May 4.

The slender shrew is a small shrew of the family Soricidae distributed in Northeast Asia. Four species of shrews live in Hokkaido, among which the S. minutissimus (S. minutissimus hawkeri) is designated as an endangered species. Because shrews have small bodies and their metabolism is so high that they cannot withstand even a few hours of fasting, long-term rearing and breeding are extremely difficult.

Establishing breeding techniques in captivity is considered important for conservation, but there are strict limits on the number of captured individuals, and research has shown little progression. While there have been reported cases of captive breeding for S. unguiculatus, which is relatively large, there have been no successful cases for small shrews like the slender shrew.

Therefore, in this research, the group aimed to establish long-term rearing and breeding techniques in a captive environment targeting the slender shrew, which has a body size close to that of S. minutissimus.

Using individuals collected in Hokkaido and individuals born in captivity, they conducted long-term individual rearing at the facilities of Sapporo Maruyama Zoo and conducted pairing experiments using individuals that reached sexual maturity. Behaviors were video-recorded and observed. They classified behaviors into three categories: "contact," "flirting," and "mounting (mating behavior)," quantified the frequency and duration of mating, and recorded body weight changes and other data of pregnant individuals.

As a result, they succeeded in three cases of pregnancy and birth. The gestation period was estimated to be 25 to 29 days, and the weaning period was estimated to be 25 to 30 days after birth. Unique mating behavior was also observed. The shrews grew from a birth weight of about 0.3 grams to 3.5 grams in about 20 days.

Ohdachi said, "The results this time began with securing live animals, including a pregnant female, through a field survey in eastern Hokkaido, and rearing her offspring for a long term at Sapporo Maruyama Zoo. Capturing wild individuals requires advanced techniques and a great deal of effort, and obtaining a pregnant individual in particular was the starting point of the research. After that, the establishment of rearing techniques and the execution of pairing by Maruyama Zoo, the detailed observation and data analysis of breeding behavior and growth processes by students from Tokai University, and the formulation of the research plan and academic evaluation by me from Hokkaido University came together, culminating in the world's first captive breeding study of the slender shrew. We expect that these results will not only become a technical foundation for the ex-situ conservation of the endangered least shrew, but will also serve as a new starting point for studying the breeding, physiology, ecology, and evolution of shrews, which have been difficult to clarify in the wild."

Journal Information
Publication: Mammal Study
Title: Breeding Behavior and Growth of Young in Captive Slender Shrews, Sorex gracillimus
DOI: 10.3106/ms2025-0020