• The shrew is the smallest land mammal on the planet
• Are among the oldest predators in the world, having evolved over 45 million years and have changed little over the past 10 million years.
• The shrew has a very high heart rate, ranging from 700 to 1200 beats per minute.

Shrews have the unique ability to shrink during winter, including the skull, spine, and internal organs. This is the so-called Denel phenomenon, where shrews do not need to eat as much food in winter due to their shrinkage and weight loss.


 Shrews have spread throughout the world, and they are one of the few venomous mammals in nature. They are also ferocious, earning the nickname "tigers of the small animal kingdom" (though their prey is usually limited to worms and slugs).

A new study has revealed something even stranger. It turns out that the skulls of the common shrew Sorex araneus, which lives in the UK, Europe and parts of Asia, actually change size with the changing seasons.

Polish zoologist August Dehnel first noticed that shrews’ bodies seemed to shrink while studying them in the 1940s,which was dubbed the “Dehnel phenomenon.” But the exact amount of “shrinkage” remained unknown. Therefore, researchers from the Institute of Ornithology. Max Planck in Germany decided to investigate this phenomenon.
Researchers captured 12 shrews and implanted them with microchips. These insectivores were then measured in summer, winter and spring.
Scientists found that the animals’ bodies shrunk by an average of 15% during the winter and recovered almost, but not quite, to their previous size in the spring. The shrew also experienced a loss of overall body mass, with brain mass reduced by approximately 20–30% in addition to loss of mass in other major organs and even a reduction in the spine. In total, body weight decreases by approximately 18% in winter and recovers to 83% in spring.