The preference of Syrian hamsters (Mesocricetus auratus) for different in-cage shelters was tested. First, 15 males and 15 females were made to choose between a cage with a shelter and one without. Different shelters were tested consecutively: short (10-cm) or medium (15-cm)
pipes made of black acrylonitrile butadiene styrene (ABS), 7.6 cm in diameter and open at both ends; and short or medium boxes made of black acrylic panels and open at only one end. The strongest use of the shelter cage for nesting (about 75% of days) was in the case of the medium, open pipe,
for both males and females. The strongest use of the shelter itself for nesting was also in the case of the medium open pipe (52% of days). A second experiment gave a choice between pairs of shelters (of seven different types) to 10 males and 10 females. Both sexes nested significantly more
in a medium pipe closed at one end than under a wheel, and tended to nest more in that medium, semi-closed pipe than in a medium, open pipe. Also, females tended to nest more in the medium, semi-closed pipe than under an aluminium cover. Other pairings did not yield significant differences.
Direct use of the shelters for nesting was rather low, except for the medium, semi-closed pipe (about 50% of days). Semi-closed ABS pipes are inexpensive, easy to clean, and do not interfere with running wheels, and they could be recommended as environmental enrichment for hamsters.