NOTE: Before reading this post, please read my earlier post Buckthorn – Invasive Plant.
Blue Snow
Who knows where the blue snow comes from? Blue rabbits? The diet of the eastern cottontail rabbit (Sylvilagus floridanus) often changes in the winter from green plants to woody vegetation. In late winter, its diet changes to all twigs and buckthorn (Rhamnus spp.). The buckthorn holds its leaves and its blue berries well into winter.
However, the cottontail rabbits don’t eat the berries. Usually the berries are either too high on the tree for the rabbit to reach, or all the berries are eaten by the birds. No, the rabbits are eating the bark and small twigs and branches of the buckthorn. The buckthorn produces phytochemicals through primary and secondary metabolism. Usually the phytochemicals have biological activity in the host plant and help with the plants’ growth or defense when fighting competing trees, pathogens such as plant-killing fungus, or predators such as insects.
“In this case, it is believed that the phytochemicals are consumed by the rabbit when it eats the small twigs and branches. The compounds pass through the rabbit’s system and come out in the urine. Normal rabbit urine color is yellow. When they are eating buckthorn, the rabbit’s urine comes out yellow, but it is widely reported (not tested) that once the urine, tainted with the phytochemicals, is exposed to sunlight, it turns blue in about ten minutes. And, therefore, you get blue spots in the snow.” (Stan Tekiela’s Nature Smart Blue Snow.)
This is called oxidation — when urine turns blue from exposure to oxygen or sunlight.
Orbed Narrow-wing Moth (Magusa divaricata)
The orbed narrow-wing moth (Magusa divaricata) is a moth species whose caterpillars feed on buckthorn (Rhamnus spp.). Native to the Americas – from eastern Canada, the southern United States, through Central America, and to South America – they migrate northward during late summer and fall, reaching as far north as Maine and Wisconsin. Known for its blackish-brown coloration with a faint white “orb” (spot) on the forewing, this species feeds on buckthorns. cata is a medium-sized (33–45 mm wingspan) nocturnal member of the Noctuidae family.
The Home page image for this blog post is a cartoon by John Klossner.
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