Stepping of the forelegs over obstacles establishes long-lasting memories in cats

its historical range extends along the subtropical coasts of both North and South America with only occasional and temporary appearances at latitudes higher than 40 degrees. The squid feed opportunistically on a broad range of surface and deepwater fish, crustaceans and squid, many of which undertake vertical daily migrations of several hundred metres pursued through these depths by the Humboldt squid, which shows that it can tolerate the much colder temperatures at these depths. In turn, the squid is favoured prey for tuna, marlins and other billfish, sharks and toothed whales. But numbers of tuna and billfish have declined substantially as a result of fishing pressure. Reporting in Proc. Natl. Acad. Sci. USA online, Louis Zeidberg and Bruce Robison at the Monterey Bay Aquarium Research Institute at Moss Landing, have studied the video observations made during monthly dives of a remotely controlled vehicle. Observations began in 1989 but no squid were observed until 1997, associated with an El Niño event and some persisted until the following year. Very few were then seen until 2002 when they returned in abundance, associated with a small El Niño event, and they have remained there ever since. Hake were also observed by vehicle cameras in abundance until the arrival of the squid. Numbers now seen are very low, the authors report. Multiple factors seem to be involved in the squid’s range expansion. “The present situation off central California appears to be that of a physiologically tolerant species with a fast generation time that has moved into a new area during a period of substantial, climatic, oceanographic and ecological changes,” the authors write.