Victoria Falls - Turns out it's not just traders who crisscross their way over borders in this part of Africa. Elephants appear to do it too - in ways not always expected, according to researchers tracing the movements of elephant populations in the wider Victoria Falls area.Lionalert.org has just published a brief summary of observation work carried out by a team of researchers on their Elephant Programme in Livingstone, on the Zambian side of Vic Falls.They've been involved in studying images taken of these giant mammals between the middle of May and the end of July in Zambia's Mosi-oa-Tunya National Park.What they've found is that a total of at least 280 elephants were seen in the area in that two-and-a-half-month period. But only a very small number - 11 to be exact - has been seen at least once every month, lionalert.org says. Even allowing for human error (the possibility that some elephants were more regular visitors but just weren't recognised by researchers), that would suggest the elephant population in this area is highly mobile.Artificial watering pans Said lionalert.org on its website: "This small proportion adds further weight to our hypothesis that the elephants swim back and forth between Zimbabwe’s Zambezi National Park and Zambia’s Mosi-oa-Tunya National Park throughout the dry season, rather than migrating over to Zambia at some point and staying for the whole season. "One group of 18 male elephants is regularly seen swimming its way from an island in the Zambezi to Mosi-oa-Tunya National Park," the group says.It's already well-known that elephants from Botswana tramp their way across the (dry) border in Zimbabwe's Hwange National Park, more than 200km from the Victoria Falls area.At the height of the dry season, elephants are attracted to the artificial watering pans in Hwange that groups like the Bhejane Trust take such efforts to keep running. Sadly, this is also when cyanide poachers have in the past been waiting to strike: four more elephants were discovered poisoned near a water hole in Hwange, Zimbabwe's official Herald newspaper reported on Monday. The latest deaths add to eight suspected to have been poisoned last month in and near the national park.Trevor Lane of the Bhejane Trust says in a newsletter released this week that it is to the credit of Zimbabwe's wildlife authority that the cyanide poisoning problem has not killed more elephants so far this year though "without doubt it will happen again." The worst toll for cyanide poisonings was in 2013, when up to 200 Hwange elephants were killed this way for their tusks.Elephants in this huge park tend to head across the border for Botswana en masse when the rains come.