Crash: A Tale of Two Species

With its armored shell, ancient anatomy, and 350-million-year lineage, the horseshoe crab almost seems too inconspicuous to stir up controversy. Yet this humble creature is at the very center of a collision between three completely different species.

For many decades, humans have harvested the horseshoe crab for use as fishing bait. Since the 1970s, we have also used horseshoe crab blood for medical purposes. But we may have gone too far. Horseshoe crab numbers have declined significantly since the early 1990’s. And, naturally, so did their egg numbers.

This is especially important to a small shorebird that is a global traveler of the most impressive kind. The red knot makes one of the longest migrations of any animal — a journey that takes it from one end of the earth to the other. To accomplish this feat, it relies on the eggs of the horseshoe crab. Without these eggs, the red knot is in danger.

In the film Crash: A Tale of Two Species, filmmaker Allison Argo tells the story of nature’s amazing ability to create fragile connections among the most unexpected creatures, and of our potential as humans to destroy those connections — or restore them.

To order a copy of Crash: A Tale of Two Species, visit the NATURE Shop.

Online content for Crash: A Tale of Two Species was originally posted February 2008.

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  • Sarah Faulkner

    Many, many thanks for this program. I’m going to use it with my classes this year for species interdependence, evolution, food webs, and, best of all, careers in the sciences. Thanks especially for providing the DVD free to me for classroom use — it is greatly appreciated and will get lots of play! Please keep up the great work.

  • yasha

    were is all ur games???????????

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  • Iva

    Many thanks for producing this program. Having once considered studying marine biology, I now know where to focus my volunteering effort.

  • Sunny

    Wonderful show. I’ve visited the NJ coast and the bird sanctuary (not paying much attention to it) at the tip of Cape May never to realize the importance or impact of what that specific center has for a global ecosystem. A WELL DONE DOCUMENTARY!!!

  • Wyatt


    I as well have a project this semester to make up a law and support it, I have chosen to make a law banning harvesting of Horseshoe Crabs for bait. I agree, A WELL DONE DOCUMENTARY!!!

  • February 8th – More Links to Horsehoe Crab & Red Knots « Prime Hook Beach Organization

    [...] 8, 2009 in Uncategorized Courtesy of PBS show, Crash: A Tale of Two Species.  This show aired last year on [...]

  • Elaine Brown

    In early 2000-2005 I had an incredible opportunity to see horseshoe crabs in the Delaware bay on Lewes beach. I have seen then in all sizes but never in the egg stage. I even rescued at least 50 from a net that this idiot man had deliberately set to catch fish on the incoming tide. He was not a real fisherman or waterman. Just someone who was lazy and didn’t want to go out and fish from a boat. He was so mad because his new expensive huge net had been destroyed by the crabs trying to escape. I was so mad at the man and told him I didn’t care about his net; but he had to help me free as many as we could as the crab’s survival was more important than his net and it served him right for trying to net fish. I feel so fortunate to have seen the crabs and help a few survive man’s stupidity. Anything that can be done to ensure the crabs and Red knots survival should be done. We are all affected every time we lose any species and someday we may not exist. Excellent documentary.

  • Virginia

    In the late 1970s-80s I was fortunate to spend part of my childhood summers at my friend’s cottage at the Maryland Chesapeake shore and the horseshoe crabs were everywhere on the shore back then. I can’t believe how these animals have suffered so much since then. I hope they find a better alternative to the pharmaceutical benefits so 12% of crabs don’t die in the process.

  • Marianna

    This documentary has a long lasting effect on me. The crualty and selfishness of humans will surely destroy life on the planet. Nothing is sacered, most societies allow to mankind to kill, torture each other and any and all animals as they pleased. Of course there is always some “great excuse” going with it. It makes me sick, very sad and angry. I can only pray that animals will never suffer as we cause them pain beyond our own imagination.

  • anna cousins

    I knew that they existed but I never knew that the Horseshoe was diminshing.

  • mramell

    When everything is gone and humans are forced to eat each other we’ll say stupid things like, “Well, they WERE here for us to eat and use. Now our dead are dying for US.” I just hope I’m long gone by then.

  • Palmer Ward

    My wife, LBB Ward, and I had a house right on the water at Reed’s Beach, NJ for over 16 years and our noticing the drastic reduction in the Horseshoe Crab population in the early to mid-nineties was one of the inspirations for her fabulous all ages novel, “Professor Angelicus Visits The Big Blue Ball.” It’s a densely educational and entertaining tour de force which explores the extreme interrelationship between all of Earth’s creatures.

  • Palmer Ward

    My wife, LBB Ward, and I had a house right on the water at Reed’s Beach, NJ for over 16 years. Our noticing the drastic reduction in the Horseshoe Crab population in the early 1990s was one of the inspirations for her fabulous all-ages novel, “Professor Angelicus Visits The Big Blue Ball.”
    It’s a densely educational and entertaining tour de force which explores the extreme interrelationship between all of Earth’s creatures and water.
    There’s a whole chapter “The Bay, King Harry, and the Shorebirds” devoted to this exact relationship.
    She was also very instrumental, through the Delaware Riverkeeper, in forcing the current moratorium on the crab poaching.


  • paul van berkel

    What do the red knots eat on their return trip at the Chesapeake?

  • Chuck

    This was a very heart touching story on the Horseshoe Crabs and the Red Knot Birds. It is time to start a program that keeps the crabs from being harvested. This will keep the bird cycle to flurish as once they did a few years ago. These species have been with us to long for us not to try and save them just as for the crabs. When we needed the crabs for wealth they were there and thankfully they are still here with us. Lets give back to them because they do have a word in this too. Man, crab, and bird come from the same world and they deserve to be here just as us humans. Excellent Sunday story.

  • Mike

    Thank you for the well done documentary. Showing the interconnection between species and how man’s interference can have deadly affects is critically important. There is no doubt that man’s impact is profound and reaches all points of the earth. While this film points to a very specific tie-in between two species and man, I hope that everyone takes a hard look at their owm impact from everyday life. Seemingly insignificant personal actions have profound affects on our environment. Everyone of us share the responsibility to find a way to live sustainably and in harmony with the ecosystem that supports us all economically and biologically. One way to do that immediately is to scrutinize every product you buy from tooth paste to your next car.

  • Marlene Zinni

    Will there be a follow-up to “Crash” regarding the status of the RedKnots on their return flight from the Artic?

  • Alan Petersen

    Fantastic episode!

  • Frankie

    Wonderful show and very educational. I will never look at the horseshoe crab the same again~

  • bdeuber

    I walked on Ave of Americas at 44st 11:45pm May 1, 2009 and saw an odd dead bird with a long beak, light brown and speckled. I thought how strange for a shore bird to be on the NYC sidewalk. Watching the show tonight I am certain it was a Red Knot. Is mid-town on the flyway and did it fall out of the sky? It was not yet stiff and not apparently mangled. It was not there tonight, pity I did not stop to take a photo.

  • Sarara

    oh thx i needed facts!!

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  • Cape May New Jersey Birds « Larry Hennessy Photography

    [...] on the Delaware bay to photograph the Red Knots. The Red Knot population is decreasing with the decrease in Horseshoe Crabs. These crabs, which are harvested for use as bait, come up on the beaches along the Delaware Bay in [...]

  • redindo

    saw the documentary only last week… it caused me to wonder…. but i always end in awe! we are their caretakers! we are given the responsibility to take care & protect them… awesome creations! ad majorem Dei gloriam! we are interconnected therefore! keep it up guys!

  • olivia

    the shows said only 13% of the horse shoe crabs do NOT surviey the blood thinG! :( poor things! they did not do anything to bother or hurt us! what did they ever do wrong?! (nothing!) i feel bad for them! i think the pepole should not be aloud to do anything to them! If the pepole who take the blood out of them should know/ feel that if that where them getting the blood out of them… it would really hurt! so the next time someone you see is taking the blood out of thme remember… just wounder…” what if that were me getting hurt and diying because they were taking the blood out of me! and only 78% of my species survived! And 17% of my spesies died of this!” just remember. just remember!


    Let’s just say I had some horseshoe crab blood, who would buy it for $15,000

  • David

    We have seen lots of horseshoe crabs and red knots near our home in West Central Florida. Will this help the reaearchers?

  • lori

    Just saw the documentary and blown away. Who knew? Great stuff, as usual from PBS

  • Craig Griffith

    I have seen these birds for the last 3 years on Saginaw Bay Michigan from the second week in may through the first week in June, most of the birds i have been seeing have been on the southeast shoreline on the bay. The water level is up this year so i haven’t seen as many as i did last year. I took alot of pictures of these birds the last couple of years.

  • debra

    I live in SC on HH Is. I see horseshoe crabs quite often and was wondering if the red knots migrate through this area? Is this information important to researchers?

  • Lenoir

    That’s one of the most powerful – and powerfully sad – documentaries I’ve seen. People: is there anything out there, any species, any ecosystem we don’t end up messing up in some way? There are times I just feel ashamed to be human. I know that sounds like a stupid and dramatic thing to say, but it’s how I feel when confronted with a story like this that shows the consequences of human idiocy and selfishness and how it irrevocably affects the other creatures around us. I wish there was something I could do to help the red knots – even if it were collating data on my computer here in Upstate NY to help the conservation efforts, I’d be glad to try. Thanks to the people out there who are devoting themselves to trying to save these birds from extinction, and those trying to increase the horseshoe crab populations. For that matter, thanks to all conservationists, who take ego, greed and short-sightedness OUT of the normal human equation and try to make things right again.

  • Barton Chittenden

    I spent a summer in college bleeding horseshoe crabs on Cape Cod. I believe that the $15,000 is for a flask of concentrated blood: the clotting proteins are found in the blood cells, which are only a part of

    The needle is inserted in a section of membrane about the size of a quarter, on top of the hinge. I don’t believe that there are many nerve endings in this membrane, the crabs don’t move much when the needle is inserted.

    Horseshoe crabs are primitive, rugged animals. I’ve seen a number of cases where significant chunks of the carapace was missing, and had healed.

  • EdFAn

    The vast majority of horseshoe crabs killed by man are used for bait. There are restrictions on the number that can now be harvested for bait. it is actually a very small percentage of the total population that die due to blood harvesting.

  • Nick McKibbin

    I viewed this program again last night. I remember going to the NJ beaches (back in the 40’s & 50′) as a kid, and seeing the “pink breasted shore birds”. And the horseshoe crabs there were hordes of them.
    Now we are faced with trying to protect a bird species that has has adapted out to the end of a twig and the reliability of it’s food source for mid-term nourishment in its migration is in doubt. It appears that the reliability of this food source (the crabs themselves) may be in doubt also.
    One of the things that makes for a species survival is adaptability – the ability to absorb a shock and find a new niche within which to adapt and grow. Redknots evidentially are very vulnerable to this because of the food factors (mussels in the Antarctic wintering zone, crab eggs in the midmigration, & insect hatch in the Arctic environs). All three are critical to it’s success as a species. It makes for a dependence on many factors that should be stable and not subject to upset. The ‘crash’ you could say is occurring at all points with this bird; as well with many other bird species..
    I believe that global warming is probably going to make the survival of Redknots much more tenuious, because of the extreme variability of the effects of warming these three environments, and changing the dynamics of the bird’s food/energy needs at these critical times in their life cycle, as with many other bird species. You’ll wind up with crows, sparrows and starlings; with a raptor or two.

  • Gahan Haskins

    This show was good. However it has some huge errors by omission.
    The Red Knot’s and the Horseshoe Crab’s survival problems are taking place in one of the most densely populated areas of the United States:
    The Delaware Bay.

    Starting with food, crab eggs for the birds, the show speaks of the medical exploitation of the crabs.
    A statistic of 370,000 taken with nearly 40, 000 mortality! and this is called sustainable!
    Lose 14% a year and you are out of business in ten years!

    The market exploitation by bait fishermen is due to the high demand for th eels and conch. FYI, EELS are in trouble too. TOO MANY HUMANS EAT THEM.
    Also mentioned are declining habitat areas due to increasing coastal development. TOO MANY HUMANS.

    Why no mention AT ALL of the massive growth of Human Population on the US East Coast and its crushing impact on many other species in the same area?

    Menhaden are being decimated by the Omega 3 fish oil industry in both the Chesapeake and Delaware Bays.
    Striped bass are once again declining.
    No mention is made of the Brazil stopover area, and Brazil has a terrible record of protecting the environment.
    Once in the Arctic, no birds are sighted and the babble of Climate Change is brought up, even though they state the mosquitoes and black flies (bird food) have hatched and they report the June temps at a chilly 36 degrees F.

    Yet “Climate Change ” is dangled like a red cape before a bull when the show itself takes most of its one hour to state the case that the reason for the birds decline problems exist IN THE UNITED STATES.

    PBS do better.

  • Dana Hessling

    What an extraordinary insight into just how delicate preservation is.
    Thank you, PBS.

  • Peter Louie

    Fascinatiing program and quite insightful and educational.

  • Gail Feltham

    I happened to stumble upon this program last night, so glad that I did, watched it in it’s entirety. Five years ago I moved to the Jersey Shore from NYC. The beauty of the two mile stretch of beach near my home is just paradise.
    And never wear headphones, the sound of the waves and the birds are the only music i need to hear. Often there are Horseshoes along the shoreline – they always draw a captive audience when the kids are out of school.
    After watching this program I feel that I have a better understanding of the delicate harmony of environment that is so vital to the survival of the Horseshoe and the Red Knot. I plan on sharing this with my family and friends – we can all make a difference if we open our eyes and our minds. Again thank you.

  • Barbara

    As a child in the mid 1960s, we would spend our summers along Rehoboth Bay in Delaware. Late in the afternoon, I would ask my parents if we could leave before “They ” came. “They” were the horseshoe crabs. They were scary and covered the entire beach when they arrived. My parents would tell me to calm down and sure enough, like clockwork, from the southern direction they would come towards us and the beach would be black. If you have had to walk through them, there would be no where to step. About ten years ago, I brought a friend back to the same beach to see this incredible sight. As I waited, “they” finally came. All two dozen. I couldn’t believe it. So sad.

  • Matt

    Does anyone know if a temporary alternative food source could be made for the Red Knots? It seems that giving them something to refuel on rather than Horseshoe Crab eggs, would allow more Horseshoe Crabs to be born, which would allow more to survive, which would return the Horseshoe Crab population back normal size faster. Once the population was back to a proper size, Red Knots could then eat the eggs again, since the balance would be returned.

  • Wendy Thorpe

    How do I protest the bleeding of the crabs? I know they return them to the wild, but 13% don’t live. How about taking less blood per crab? Also, about the Knots, how about leaving food for them so more crab eggs survive? Where do I go to mention that? You were on the right track making artificial food for the eels, so that fisherman wouldn’t use crabs, especially females for bait.

  • Lois

    I had the same questions in my mind as Matt and Wendy, about temporary alternative food for the red knots and taking less blood per crab. The show said that about 1/3 of their blood is removed. Have they studied how many more would survive if they took less, maybe 20 or 25%?

  • Lois

    One more comment: I loved watching the footage of the developing and baby horseshoe crabs! Wonderful photography, on this and throughout the show.

  • D33dog

    It’s great that you aired a show about the horseshoe crabs. Having grown up on Long Island waterfront,I can say that there has been a sharp incline in the number of horseshoe crabs over the last 40 yrs. I’m not certain if it’s pollution or people taking them for bait in lobster/crab pots,but I hope the show opened some eyes.
    Is there any way that individuals can help cave these crabs? If there was some program near me,I would surely volunter.

  • Jason

    I just got back from my honeymoon on Hilton Head Island and saw a horseshoe crab on the shore during the day during low tide. He was just hanging out in the waves coming in and out. I didn’t know what it was, or whether it was still alive. Got some cool pictures and left it be. It was very a very cool sight!

  • Forest

    Great story! Hopefully the efforts of the people involved in trying to save the birds will be successful. I look forward to a follow-up story in the future; surely there are plans for further reporting on the status of the birds (and the crabs).

  • Liz

    I received a certificate of participation and little HS Crab pin from the US Fish and Wildlife Services Cooperative Horseshoe Crab Tagging Program for sitings on Bayville Beach Long Island Sound, NY recently. This is a facinating story.

  • Raymon Mcquigg

    great info! thanks for this.

  • meemee

    horsecrabs r cool

  • Mrs Malkan

    Thanks for the Wonderful movie, photography and nice educational show.

  • CZhang

    Thank you so much for this program. I’ve loved this show for years! <3

  • candela

    Thanks for sharing this episode.
    I hope we can still save this beautiful alliance between the horseshoe crab and the red knott.
    Its true, they depend on us and society needs to stop watching stupid TV shows like Charlie Sheen and Snookie and get more well educated about nature and how to save wild life.
    People wake up!! Global warming affect us all and it takes action from people to prevent these disasters.
    Wake up from your bubble!!!

  • Nancy Berman

    I just finished watching this episode and cried. I grew up on the Jersey Shore and always had a fondness for Horseshoe Crabs. I now live close to the beach in St. Augustine, Florida. Here, anyone who lives along the beach
    must have blackout curtains in their homes and no outside lighting used during the Spring and Summer months. We are experiencing shortages in our Sea Turtle populations. Any light on our beaches confuses the turtles when they come on shore to lay their eggs and can lead to death. (They can’t find their way back to the water.) I hope the people in Delaware and New Jersey are complying to the rules to save the Horseshoe crab thus, saving what is left of the Red Knots. For every creature we destroy on earth, many more die than perhaps we even knew existed.

  • Isabella

    Anyone in the NYC area can volunteer as a citizen scientist to help tag and monitor the HSC. Goto for more details. DE and NJ have similar programs. Let’s all help spread the conservation word and chip in if possible.

  • taylor penn

    great movie!

  • julia

    my science teacher showed this to us just to do it and i decided to write a paper about it and imma give it to her when im done and i hope she likes it!

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    My spouse and I stumbled over here by a different page and thought I may as well check things out. I like what I see so now i’m following you. Look forward to looking over your web page again.

  • jay

    i was amazed on the red knot because of what they can do.and there is no species like that in our country but it sad to say that they were facing a massive diclined on their population today.hope to give action for this…

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  • Joss Klevins

    OK.. I understand most of what you are saying but it is a lot to digest. I know it will sink in later on. Your writing is concise and to the point. By the way, Crash: A Tale of Two Species – Introduction – Horseshoe Crabs, Red Knot Shorebirds | Nature | PBS was a great choice for a title.

  • Anonomous Fisherman

    I was actually called by PBS to participate in this program. I have supported my family for over a decade harvesting horseshoe crabs and have a tremendous respect for them.

    They are tremendously resilient, more so than any other creature I know. I have always felt that the blood industry/fishery is a sustainable fishery, the 10% loss is negligible compared to the 100% loss of the bait fishery.

    The crab population is completely sustainable at the 10% loss rate, probably even at 20 or 25%.

    Imagine how all you bleading heart folks would feel if they had to do things the way they did before lysate.

    Animal testing! fuzzy furry critters injected, and killed, actual mammals, not overgrown insects, hundreds of thousands of them caged up until they met their demise.

    Chalk another one up for the bleeding hearts, damn chicken and fish eating hypocrites!

  • Chris Bowden

    What about turtles? I was at West Point Beach, today 5/28 and about 20 turtles were just hanging close off shore. Is this time for them to come out and lay eggs?

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