A tiny chalk drawing of a lion by Rembrandt recently sold for the record-setting price of $18m in New York City to benefit the conservation of big cats.

After selling at a Sotheby’s auction Wednesday, Young Lion Resting shattered the previous mark for the most expensive drawing by the 17th-century Dutch painter ever auctioned: the $3.7m Portrait of a Man with Arms Akimbo.

Young Lion Resting’s sellers Thomas Kaplan – the billionaire US philanthropist – and his associate Jon Ayers said they were dedicating the proceeds generated by the auction to their prominent wildcat conservation charity, Panthera.

“Wildlife conservation is the one passion I have which surpasses Rembrandt – and I want to attract more people to that cause,” said a pre-auction statement from Kaplan, who along with his wife, Daphne, entered the year owning 17 paintings by the baroque artist. “I can think of no more fitting way to do so than to allow this magnificent drawing, which our family has loved for so many years, and which carries so much personal meaning to … Jon Ayers and me, to go on to its next home … in services to Panthera.”

A separate statement from Ayers said “a work that so vividly captures the soul and spirit of lions … now will help protect their living counterparts”.

“I can think of no finer legacy for this masterpiece than to serve the survival of the species that inspired it,” Ayers added.

As Sotheby’s put it, the artist, whose full name was Rembrandt Harmenszoon van Rijn, was in his early to mid-30s and at his creative peak in Amsterdam when he drew Young Lion Resting. The 4.5in-tall work depicts a lion at rest – in three-quarter view – while wearing a leash around its neck, “suggesting it was drawn from life”, the auction house said in a statement.

“Every stroke renders the lion in exquisite detail, capturing its form but also its vitality, poise and power,” Sotheby’s statement added.

Being able to see a live lion would have been rare in Europe at the time, and Sotheby’s speculated Rembrandt may have had the opportunity to do so at a fair.

He is known to have drawn only six lions. Beside that which was auctioned off by Kaplan and Ayers, two are at London’s British Museum and the other four are at Paris’s Louvre, Amsterdam’s Rijksmuseum and Rotterdam’s Museum Boijmans Van Beuningen.

Kaplan co-founded Panthera with wildlife biologist Alan Rabinowitz, and Ayers is the chair of the organization. Panthera is generally dedicated to ensuring the future of the 40 species of wild cats as well as protecting the landscapes on which they depend.

Among other things, the group says it also collaborates with local communities to stop poaching and fight the illegal wildlife trade.