In many countries animal rights groups decry the many thousands, even millions, of animals used in medical experiments. In Germany, activists have adopted a new tack: focusing on the even larger number of animals that never make it into an experiment—perhaps because they don’t meet the criteria for a study or were created in the course of breeding a new research strain—and are killed to save space and money.
Science has learned that prosecutors in the German state of Hesse are now investigating whether the culling of such “excess” research animals by local universities and other institutions constitutes a crime. The probes were launched after two German animal rights groups filed multiple complaints with the prosecutors in June 2021 arguing that this killing violates the country’s strict animal protection laws, which forbid hurting animals without reasonable cause. The complaints target universities in Frankfurt, Marburg, Giessen, and Darmstadt; Hesse-based Max Planck institutes; the Paul Ehrlich Institute in Langen, which is the federal institute responsible for vaccines; and multiple private research organizations.
One complaint, involving 222 small fish killed by a company because it allegedly had no room for them, has already been dismissed. But spokespeople for the prosecutor’s offices in Frankfurt, Giessen, Marburg, and Darmstadt confirmed to Science that investigations into other allegations continue, with the Frankfurt general state prosecutor’s office coordinating the matter.
The stakes are high: Germany’s animal protection laws, which together with EU regulations govern animal research, subject those who kill vertebrates without a proper reason to fines or up to 3 years in prison. “The community is extremely concerned,” including the keepers who cull the animals, says Andreas Lengeling, who is responsible for animal research at the Max Planck Society. “The mood among researchers in Germany is grim,” adds Jan Tuckermann of Ulm University, a hormone researcher who is also on a local commission responsible for approving animal research. In response to the complaints, some institutions are already seeking to reduce the number of surplus animals by creating research strains more efficiently and matching supply to demand. “I know clients who are considering relocating animal breeding abroad,” adds Matthias Dombert, a lawyer in Germany who advises research organizations on the issue.
Two years ago, the European Union estimated that in 2017, when EU labs used 9.4 million animals in experiments, 12.6 million lab-reared animals, about 83% mice and 7% zebrafish, were culled without any studies of them. About one-third of those excess research animals had been bred and killed in Germany, the Federal Ministry of Food and Agriculture has estimated.
Germany’s debate over excess research animals was fueled in 2019 when a high court ruled that vertebrates can’t be killed simply because of economic reasons. The case involved not research animals, but male chicks, which worldwide are routinely killed in egg-production facilities that only value hens. Because such culling had been common practice for decades in Germany, the Federal Administrative Court ruled that a transitional period was appropriate, which encouraged development of methods to sex eggs; the chick culling wasn’t outlawed in Germany until January. Prosecutors and courts have issued no criminal sanctions so far.
Still, the 2019 verdict caught the attention of those opposing animal studies. “It’s known for a long time that animals are killed in labs because they are not needed,” says Silke Strittmatter, research associate at the nongovernmental organization Doctors Against Animal Experiments, which filed the criminal complaints together with the German Juridical Society for Animal Protection Law. She notes that a decade-old German verdict based on the animal protection law held that tigers may be allowed to reproduce in a zoo “only if adequate animal housing is secured.” The same principle should apply to other animals, she says. Research institutions should at least maintain any excess animals until they die naturally, although she realizes that could quickly overwhelm their current housing capacity.
Institutions can’t reasonably house that many animals for so long, according to Lengeling. He says authorities accepted the cullings, typically performed with carbon dioxide for mice, at least until the animal rights groups made it an issue. The criminal complaints “caught everyone including the legislature, which didn’t intend it that way for laboratory animals, off guard,” Tuckermann says.
The German Research Foundation says culling should be allowed under the country’s laws if animal housing, or the personnel needed to maintain the animals, is limited and the space is needed for actual research animals. It nonetheless recommends considering alternative uses of the excess animals.
For now, Tuckermann says, his research group has stopped culling excess animals—until their animal housing runs out of capacity. Meanwhile, his group has reprogrammed its software for managing lab animals: Previously a user could re lease animals for killing with the click of a mouse, but now the software requires the user to consider other options, such as transferring animals to different labs or using them for teaching purposes. Some German scientists have even wanted to offer unused genetically modified animals to zoos to feed their creatures, although regulations may prevent that.
Better matching the supply of research animals to the demand could also reduce cullings. CRISPR or other gene editors can be used to create modified animals in a single generation, without breeding several generations of surplus animals. And labs can substantially reduce the number of animals killed by thawing frozen sperm or embryos as needed, for example, rather than creating populations of surplus animals to keep modified lines going.
Ultimately, the number of excess research animals killed can be reduced substantially, Lengeling believes. “Maybe we can halve it.”
Some institutions have reported progress. Goethe University Frankfurt says that since 2017 the number of lab animals not used for research decreased by almost 30%. Other German institutions contacted by Science stress that they are trying to reduce those numbers as well.
It’s not clear whether the animal welfare groups’ tactic will move beyond Germany, as other countries have less strict animal protection regulations and often less transparency. In the United States, not even the number of animals used for research is known; estimates vary from 10 million to more than 100 million annually. As a result, U.S. labs “can kill excess animals with no need to justify (or count) numbers to anyone other than the in-house ethics committee,” says veterinarian Larry Carbone, a visiting fellow at the Animal Law & Policy Program of Harvard Law School.
In a few U.S. states, he notes, institutions must try to find new homes for healthy lab dogs and cats. For millions of genetically modified mice and zebrafish, that’s hardly an option, though.
Meanwhile Tuckermann, Lengeling, and others are wondering what the criminal complaints mean for the future of animal research in Germany. They are calling on German politicians to clarify the animal protection regulations so they know when—and whether—any culling is acceptable. “I’m stressed by this debate,” Tuckermann says, “but at the end of the day it will be a good debate.”
The German newspaper Die Zeit is publishing its own version of this investigation today.