I am quite a bit gutted. Devra Kleiman, one of the founding mothers of modern conservation biology, passed away last Thursday.

I have known about Kleiman’s work ever since my time as an undergraduate and when I began writing about pandas I was thrilled that I’d have an excuse to talk to her. Kleiman, you see, was a pretty important figure in the giant panda’s story, carrying out some groundbreaking research on Richard Nixon’s pandas Hsing-Hsing and Ling-Ling, residents at the National Zoological Park in Washington D.C. from 1972 to the 1990s.

Kleiman was, in fact, one of the first people I approached for an interview in March 2009. I had heard that she had cancer but she willingly gave me her time. It was an extremely enjoyable conversation. At one point, I asked her if she remembered a memo she’d written to then zoo director Theodore Reed in 1976. She was stunned. “How did you know about that?” she asked. I told her that I’d read it. Kleiman, only a few years earlier, had been through all the records that she’d kept over the years and deposited the most interesting stuff with the Smithsonian Institution Archives. And it was one of the many fascinating documents I found there when I spent a couple of days going through some panda folders there in (I think it was 2007).

Since the Nixon pandas’ arrival in 1972, the pressure had been mounting on staff to get the pandas to reproduce. Nobody had yet realised just how difficult this would be. Reed had rather rashly promised the nation that a baby panda would be born in 1976 to coincide with the 200th anniversary of the United States Declaration of Independence.

As it turned out, the pandas were not brought together until Ling Ling’s heat was almost over. Reed was furious. Kleiman, who was then in charge of efforts to get them to breed, offered an explanation. Ling Ling’s estrus had come several weeks earlier than the previous year. “This caught me (and I think, others) off guard,” she wrote to her boss in a conciliatory memo, the one I found in the archives. With plenty of staff carrying out round-the-clock observations according to the now well-practiced protocol, Kleiman had been confident – too confident – that any changes in Ling Ling’s behaviour would be detected. They weren’t. “I was insufficiently flexible in my attitude and much too conservative,” she told Reed. “Needless to say, I apologize.”

It is a very unusual document and Kleiman remembered writing it as if it had been yesterday. She had been brave enough to take total responsibility for the 1976 episode (even though Reed should probably have shouldered most of it for making such a rash promise). Braver still, she had selected out her apologetic memo for the likes of me to pore over at the Smithsonian Archives. She laughed long and hard that I’d found it and found it interesting. She might have thrown it away. I am glad she didn’t.

Kleiman was so friendly and forthcoming that I asked if she would read through a few of my chapters to be sure they tallied with her recollection of several important events. I sent her several chapters earlier this year and she got back to me on 12 April with some very helpful comments and suggestions. She never mentioned her illness. I never asked. According to a Washington Post obituary, she died a couple of weeks later at the George Washington University Hospital.

Amongst many professional achievements, Kleiman pioneered the field of reintroduction biology with her work on golden lion tamarins. One of my last questions to her was about reintroduction and its possible role in panda conservation. Even after a career dedicated to connecting up zoos with the conservation effort (which included penning several reports on reintroduction and pandas) she signed off her last email to me with the following sentence.

I need to think a bit more about reintroduction.

Devra Kleiman dies