Eight mallard ducks were given thousands of eggs from two invasive carp species by Vincze and her colleagues in the lab. About 0. The team discovered that 18 out of 8,000 eggs, or 2% of the total, remained intact following defecation. The researchers report their findings in the Proceedings of the National Academy of Sciences on June 22. Some of those eggs contained wriggling embryos, and a few eggs hatched. Whether eggs survive in this manner in the wild is still unknown.
Despite the low number of surviving eggs, they may accumulate, making bird droppings a potentially significant means of dispersing fish. According to Vincze, a single carp can release hundreds of thousands of eggs at once. Additionally, a vast number of mallards and other water birds may feast on those eggs throughout the world.
“It has long been a mystery how these remote bodies of water can support fish populations,” notes Patricia Burkhardt-Holm, a fish biologist at the University of Basel in Switzerland, who was not involved in the research. According to her, this study demonstrates one way that water birds might spread fish.
For fish eggs, getting gobbled by a duck kicks off a harrowing journey that includes a pummeling in the gizzard and an attack by stomach acids. But a few eggs can exit unscathed in a duck’s excrement, possibly helping to spread those fish, including invasive species, to different places, a new study finds.
Bird droppings, feet, and feathers can disperse invertebrates and hardy plant seeds (SN: 1/14/16). Orsolya Vincze, an evolutionary biologist at the Centre for Ecological Research in Debrecen, Hungary, notes that because many fish eggs are soft, scientists weren’t expecting them to survive a bird’s stomach.
The researchers purchased eight captive-bred mallard ducks from a nearby breeder and two species of carp eggs from an aquaculture institute in order to test their hypothesis. Over the course of two different experiments, they force-fed each duck three grams of fertilized eggs (roughly 500 eggs per serving) from each species of fish. 18 complete eggs were found in the bird feces after examination, and the scientists put them in an aquarium. Three of the twelve had developed into healthy baby fish after viable living embryos.
For centuries, scientists conjectured that fish eggs could enter remote lakes and ponds by traveling on the feet or feathers of water birds. However, research published in July in the Proceedings of the National Academy of Sciences USA suggests that the mode of transport for some eggs may be much more intimate: the study offers the first proof that eggs with soft membranes that are consumed and excreted by birds can still hatch into young fish that are viable.
According to co-author Orsolya Vincze, an ecologist at the Danube Research Institute in Debrecen, Hungary, “nobody ever really thought of bird guts before because I think its quite an absurd thing.” “We still believed it was highly unlikely, but we were hopeful we would find something.” In 2019, a killifish egg from swan excrement was successfully hatched by researchers; however, killifish eggs are remarkably resilient and can endure prolonged periods of dehydration.
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