The Emus of Tower Hill eat Capeweed
Pretty much exactly as the title said. The population of emus that live in Tower Hill, Victoria, Australia eat the flowers of Arctotheca calendula aka Capeweed as a food source. Capeweed is an invasive species, not native to Australia.
To my knowledge, this specific animal-plant interaction has not been documented before. I have been wanting to add more observational posts like this one to my blog, so at least here's a start. Hopefully one day I will be able to filter all these posts using a #observation tag.
This was the first time (I fully remember) seeing an Emu in the wild. I may have seen them as a kid on holiday briefly. Not sure. This observation occurred during a roadtrip to Adelaide via the coast. I stopped at a beautiful dormant volcano, Tower Hill.
All of the folowing photos were taken early-afternoon on 18/10/25.
The Observation
I first noticed a pair of emus crossing the Tower Hill Lake.
As usual for this time of year, the Capeweed was in flower. In general, it dominates in areas that have been mowed for lawns (usually flat areas). It's tough for any plant to thrive when they are chopped every couple weeks - or alternatively if herbivores/omnivores graze on them.
As you can see, it's able to really carpet an area. From what I observed, the emus exclusively ate the flowers. The whole thing too. The stalk, the petals, the stamen/anthers, everything.
I tried to get a picture of this, and got one! If you look in the mouth of the emu in the photo below, you just make out the capeweed flower entering the mouth (click here for bigger image).
I observed them eating Capeweed (and nothing else) for around 40 minutes, indicating a clear preference, or at least strong dedication to eating this food. There were very few breaks. They only stopped gorging themselves if they sensed a person was close to them, at which point, they would look up directly at you, as a sort of courteous way to say 'back off'. Their gaze had this subtle but lingering undertone of assault, or like aggression. It's hard to explain, but this is how I felt.
Then came another emu, doing the exact same thing. Given there's now two emus eating capeweed, this rules out the possibility that it was just one individual, an odd unit, having a munch. It leads me to assume the entire population of emus at Tower Hill, would be doing the same thing. I feel fairly confident in this.
I don't think these two are a couple. Emus have sexual dimorphism and females are larger, darker and heavier than males. Not fully sure, but I think these are both males.
Emu relationships are interesting. I initially thought they formed strong bonds to each other - and this is true. But it's one of those things where the more I look into it, the more complex the answer becomes. There's monogamy, polyandry and promiscuity. In fact it's rife for drama! Females may even fight vigorously among themselves for access to unpaired males. Whilst the females lay the eggs, the males will incubate the eggs (up to 60 days) and look after the young birds once they hatch.
Other thoughts
Then I realised another interesting connection. Capeweed is a South African weed. And in South Africa there is another (and prehaps more famous) big flightless bird...
The Osterich.
Would osteriches eat this weed too? Could it be that emus are taking advantage of a weed, partly due to their shared evolutionary history with osteriches (both being Ratites). Have emus sort of pre-evoloved (or are somehow predisposed) to eating this weed? Can I trace the emus food preference for Capeweed back to some early shared ancestor? After all, South Africa and Australia were once part of the super continent of Gondwana.
My answer to my own question
In short... no.
It is crucial information to know that both Osteriches and Emus are omnivores. They eat plants, but also insects, meat, eggs, seeds and fruit. They are real generalist eaters.
It is true, each year emus do exploit the flowering period of Capeweed. However I contend that this is simply a behavioural response to their environment, and cannot be traced back to a shared ancestory with osteriches. In fact I don't think emus have a real preference for this specific daisy species (Arctotheca calendula) over any other daisy species in the family of Asteraceae.
Emus eating Capeweed makes sense from a behavioural perspective. Capeweed doesn't flower all year. So when an invasive weed suddenly becomes an abundant food source, readily available. Why would you spend energy and resources searching for other food (if you were an emu that is)?
Emus are just exhibiting their foraging behaviour. Consider before Capeweed entered Australia. The vegetation would have consisted of numerous native daisy species, eg, Murnong, Senecio, Vittadinia and others, likely similar to Capeweed in terms of nutrition and edibleness. I'm sure Emus still eat these native species now too, it just happens to be that these native species no longer exist in some areas as they were outcompeted when Capeweed invaded.
This observation would be much more remarkable however if both birds had a narrow range of food preferences. If this was the case, then the observation of Emus eating Capeweed would be much more significant, and may suggest something more. I still think any evolutionary reasoning as to why Emus eat Capeweed is a shaky, unconvincing argument. I am going to refer to the rule of parsimony or occam's razor for this one. This states that the most simple solution is usually correct.
I believe emus eating Capeweed is a behavioural response to their environment, and cannot be linked back to some early common ancestor between osteriches and emus. Despite all this, the idea kept me entertained me for while and was nice to think about.
In a previous blogpost I wrote about Corellas, Galahs and Cockatoos eating onion grass, and whilst this is analogous in some ways, it's also different. In previous post, there is an obvious learned behaviour (the birds physically dig up the corms). In this case, the emus are just foraging, as they have always done, as any bird has done, since forever.
Finally, the next time you find yourself on a roadtrip in Australia have a look out for emus. Whilst emus are easier to find, know that there are a few ostriches roaming around in the outback too!