Upon returning from recess, senators received something that they've never gotten before: six endangered species condoms.

The environmental organization Center for Biological Diversity sent the condoms — each featuring a slogan such as "Wrap with care, save the polar bear"* — as part of its campaign for World Population Day, which falls on Tuesday.

This particular campaign was to raise awareness about human population growth, but also was sent to urge senators to vote in favor of reproductive rights and family planning programs, said Leigh Moyer, CBD's population organizer.

"We opted to focus on the Senate precisely because they are deciding on health care that has the potential to hurt millions of people, especially women," Moyer said in an email. "...We sent condoms now because World Population Day is a great opportunity to draw attention to the connections between decisions in Congress, human health, reproductive rights and, even, wildlife extinction."

CBD started its endangered species condom project back in 2009, as a way to start a conversation about how the growing human population and overconsumption affect the planet. Since then, the organization has distributed 10,000 or more condoms annually around the country.

This year marks the first time condoms have specifically been sent to Congress. The package of six condoms was accompanied by letters that either applauded or admonished senators for their stances on reproductive health care.

Sen. Ben Sasse, R-Neb., noted the arrival of the package at his office last week.

"We believe that the solutions to human population growth and the impact it has on the environment is based in human rights, universal access to contraception and education for women and girls," Moyer said.

*For your enjoyment, here are the slogans on the condoms: