Without intervention, the viperine water snake would probably have choked on the invasive fish and died.
An adult viperine snake, Natrix maura, was photographed attempting to eat an invasive ruffe (Gymnocephalus cernua), a small bait fish native to much of Europe and Asia, but is considered an invasive species in southeastern France, North America and other European countries.
Figure 1. Predation attempt by Natrix maura on Gymnocephalus cernua in Lac of Carcés, southeastern France) (A) Location of Lac of Carcès. (B, C) Natrix maura experiencing difficulties while attempting to ingest an individual Gymnocephalus cernua. (D) The Raffe, Gymnocephalus cernua, showing its dorsal spines. Photos by Nicolas Fuento.
Natrix maura is a fish-eating snake native to much of southwestern Europe and northwestern Africa. In 2018, Herpetologists Nicolas Fuento and Grégory Deso photographed the viperine snake in southeastern France as it attempted to ingest the ruffe, which is a small fish that is often used for bait by anglers.
“The snake showed unusual spasmodic movements in an apparent attempt to expel the fish, which appeared to be lodged in the snake’s oesophagus (Fig. 1C). After several minutes of observation, with the snake’s movements slowing, the fish was manually removed and identified as a ruffe (Fig. 1D),” the researchers wrote in Herpetology Notes. “The fish was dead, and its dorsal spines had become stuck in the upper part of the snake’s oesophageal wall. Although in several cases snakes can survive injuries caused by fish spines (Kornilev et al., 2022), we cannot confirm that in this case the snake would have survived without our aid.”
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The researchers note that several invasive fish species in Europe cause mortality in fish-eating snakes. These include the largemouth bass, brown bullhead, and common sunfish. These North American species have caused mortality in both Natrix maura as well as Natrix natrix, also known as the grass snake or ringed snake. They also note that Natrix tesselata has a penchant of feeding on the invasive Prussian carp in Turkey. These snakes have also learned to avoid these alien fish, or are preyed upon by larger snakes.
Natrix maura, according to the researchers, is in decline in its natural habitat. The invasive ruffe does occur with the fish eating snake in Mediterranean wetlands, though the snake is rare and in decline in these areas. Previous research has stated that the mortality risk for this species in ingesting the non native fish can have negative effects to its conservation status. They note that more research should occur in this regard, especially in declining snake populations.
Natrix maura Information
The viperine water snake is semiaquatic and is known to target fish, frogs and other aquatic prey items. While it looks like an adder, and is known to behave and strike like an adder but doesn’t bite. It is found in Portugal, Spain, Andorra, France, northwestern Italy, and Switzerland and northwestern African countries including Morocco, northern Algeria, northwestern Libya and Tunisia.
It is gray, brown or reddish in coloration with a black vertebral stripe that zigzags. It features keeled dorsal scales and can grow to 33 inches in length. The snake is also invasive in Mallorca, where it preys on the Perez’s frog (Pelophylax perezi). It has also caused the Majorcan midwife toad (Alytes muletensis) to abandon its native range in favor of ecosystems that are too steep for viperine water snake.
The paper, “The introduced Ruffe, Gymnocephalus cernua (Linnaeus, 1758), a new potential threat to fish-eating snakes in Western Europe” can be read on the Herpetology Notes website.
