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IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 51COMMENTARY

Since 2002, Fundación Biodiversidad (FB) has conducted a
management program for Yellow Anacondas (Eunectes

notaeus) in Formosa Province, Argentina. The main objective of
the program has been to establish a sustainable-use model that
ensures equity among users while promoting research and con-
servation of the resource. Recently, Rivas (2007. Iguana 14(2):
74–85) criticized the program in the context of his opinions
regarding the impact of global economic development on the
conservation of Green Anacondas (Eunectes murinus). Although
we provided a detailed review of the Argentine program (Micucci
and Waller. 2007. Iguana 14(3): 160–171), we believe a more
specific response to his comments is appropriate and necessary.

Rivas’s views are based almost entirely on a brief visit he
made during September 2002 to Formosa, at the end of the first
experimental hunting season. He was seeking images of Yellow
Anacondas for a National Geographic Channel (NGC) docu-
mentary. Two years later, FB was invited to review the
“Objective Anaconda” script with a commitment of “… not
putting on-air the documentary until all comments were taken
into consideration” (V. Linares, in litt., NGC — Research,
Standards, & Practices, 30 March 2004). Since the most ques-
tionable opinions were made by Rivas on-the-air, this apparent
compromise was not adequately addressed, and the final prod-
uct was, at least, controversial. In reviewing his recent article in
Iguana, we quickly came to the conclusion that, in these subse-
quent years, he has chosen not to inform himself properly
regarding the basics of the program, which would have allowed
him to support his position with facts instead of errors and mis-
conceptions.

Specifically, Rivas stated that the Argentine program pro-
motes the hunting of specimens larger than 2.3 meters, not spec-
ifying if this size relates to skin size, snout-vent length (SVL), or
total length. He also mentioned that hunting takes place “... at
the beginning of the warm season...,” when, in fact, the Program
allows local people to harvest snakes above 2 m SVL during the
local winter (June–August). Additionally, Rivas stated that the
skin minimum size limit established (2 m SVL = 2.3 m skin
length) responds to a commercial requirement for large skins.
On the contrary, the current skin size limit was established as a
control variable (Micucci et al. 2006). Historically, specimens
over 1.3 m SVL were hunted with no additional considerations,
affecting all size classes in the population; the 2-m limit reduced
by half the snakes vulnerable to hunters. Logically, the interna-
tional markets prefer large hides (this is true of all reptilian
species in the skin trade); the coincidence between market pref-
erences and program requirements is circumstantial but advan-
tageous because it warrants economic sustainability.

Further, Rivas provided a simplistic analysis of the pro-
gram’s economics by referring to what he called “the lion’s share”
of the income going to the private sector. However, on the ‘cost’
side of his analysis, he only took into consideration the price of
the skins paid to hunters (in 2002), but forgot to mention the
other costs that are paid by the private sector (e.g., program
research and running expenses, logistics, freight, state and
national taxes). Rivas’s logic falls apart if we apply the same cri-
teria to other examples, such as comparing the price of a valued
fish on a fancy restaurant menu to the cost of that fish paid at

C O M M E N T A R Y

Anaconda Conservation: 
A Reply to Rivas

Tomás Waller and Patricio Alejandro Micucci

Fundación Biodiversidad, San Martín 945 piso 3 #23, Buenos Aires, Argentina C1003AAS

Yellow Anacondas (Eunectes notaeus) harvested as part of the Yellow
Anaconda Management Program (YAMP) in Formosa Province,
Argentina. Snakes are held alive for biological studies before being
killed and skinned.

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52 IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008

acquisition from the fisherman. Rivas implied that the program
failed to ensure resource (land and snakes) protection without
providing any evidence — and based only on a weekend-trip
during the first year of the program! He ignored the realities that
the La Estrella marsh is an area protected by law since 2005 and
that the anaconda harvest program is the only operation permit-
ted in that wetland. Another misconception occurred when he
proposed that  “... the program was less of an effort to manage
anacondas than an economic enterprise using anacondas as a
capital commodity...” We see no contradiction in managing ana-
conda populations for selling skins to benefit local people and
committed investors, similar, for example, to programs that
ranch and harvest alligators in the United States, crocodiles in
Cuba, or caimans in Venezuela.

This author also stated that the program resulted solely
from a proposal by the private sector in Formosa in response to
the 2002 breakdown suffered by Argentina. This is, to say the
least, false and absurd. FB conceived and proposed the Yellow
Anaconda program as an alternative to the historical misuse of
this living resource that had been exploited without restrictions
for more than 60 years! Rivas chose to ignore decades of tradi-
tion of Argentina as a wildlife exporter (e.g., up to 1 million Tegu
lizard hides/year and 300,000 fox hides/year) and demonstrated
considerable naivety by suggesting that the impact of the harvest
of 5,000 Yellow Anacondas per year would modify the course of
the nation’s or even the province’s, economy! In addition, his
interpretations of national or provincial competence at manag-
ing natural resources are simplistic. Since the Yellow Anaconda

WALLER AND MICUCCI

Emergent logs and logs covered by climbing plants, locally known as “champas,” are preferred basking sites of Eunectes notaeus in La Estrella marshes
in northeastern Argentina. Snakes seek these microhabitats during the winter, when water temperatures drop to 15 °C or lower. Both males and
females need warmer temperatures to complete gonadal cycles before the onset of the mating season in spring.

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Yellow Anacondas (Eunectes notaeus) are most vulnerable to collection during the winter when they are cold and leave the water to bask.

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IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 53COMMENTARY

is a CITES (Convention on International Trade in Endangered
Species of Wild Fauna and Flora) Appendix-II species, the gov-
ernment’s only responsibility is to assure compliance with Article
IV (non-detriment finding) of the Convention.

Rivas affirmed that the program harvests mainly female
snakes. Although 75% of the animals harvested are females, the
rationale for this practice does not correspond to his unsophis-
ticated deductions. Instead, this proportion results from the
interplay of a minimum size limit, the species’ natural size dis-
tribution, and a pronounced female-biased sexual size dimor-
phism (Micucci and Waller 2007). If the minimum size were
reduced in an effort to reduce the proportion of females versus
males taken (presumably because more males would be hunted),
the actual result would be an increase in the absolute numbers of
females harvested, since allowing smaller animals to be taken
would inevitably entail the sacrifice of young and small adults of
both sexes that currently are protected by the program.
Ultimately, what matters is the actual proportion of females
taken from the population, which we estimate to be less than
5%. Rivas also erroneously stated that pregnant females are dif-
ferentially affected by the harvest, on the assumption that gravid
females are most visible when basking. However, at our latitude
the harvest occurs during the cool winter months, exactly when
the species is not reproducing, a fact that he as an anaconda spe-
cialist should not ignore. At the end of his article, he affirmed
that local hunters “... anticipated a sharp decline in anacondas...”
This comment, aside from a lack of scientific rigor, is far from
reality, since, five years after his visit,  the 2007 harvest season
generated record results — without significant changes in skin
size or sex structure of the population.

We consider that Rivas’ article was fostered by an exagger-
ated concern for anacondas. According to CITES statistics, cur-
rent volume in trade is null or negligible compared to historical
records and aquatic habitat destruction has been slight on a
global scale, especially when compared to the fate of terrestrial
ecosystems. Consequently, we believe that Rivas exploited these
“TV-fashionable” animals in order to express his personal views
on the world economy and his prejudices against wildlife-utiliza-
tion policies that he rejects for subjective reasons. For example,
his statements that management under sustained yield models

(i.e., Yellow Anacondas in Argentina, most fisheries) demands a
previous assessment of a species’ population size and intrinsic rate
of increase and that obtaining basic biological data is a prerequi-
site for management are both readily disputable. Sustained-yield
models were devised to manage non-easily assessable populations
(like most fisheries) and, due to the feedback that management
provides, estimates of basic demographic parameters like abun-
dance and rates of increase are then possible (Caughley and
Sinclair 1994). In fact, management decisions rarely result from
pure research (Webb 2002), and the “adaptive management”
concept (Hollings 1978) evolved to overcome the usual insur-
mountable difficulties that represent acquisition of basic demo-
graphic parameters as a prerequisite for wildlife management.

Rivas opined that some practical conservation initiatives are
laudable, but that conservationists would be more effective in
achieving conservation goals by subscribing to anti-globalization
movements is non-realistic. Predicting the outcome of changing
economic policies that are not expected to be realized for 25–50
years is impossible (Wallerstein 1999). Moreover, opposition to
economic changes does not provide solutions for wildlife conser-
vation, as the main concerns of such movements are socio-eco-
nomic in nature, and have little to do with human population
growth and its effects on wildlife and habitats. Although we totally
agree that the world’s emphasis on development at all costs fails to
address many crucial issues, we are simultaneously convinced that
practitioners of conservation should address actual problems with
available tools and technologies in order to be effective. Boycotting
current conservation strategies in favor of ideological utopias is
both ineffective and discouraging. If I suffer from a smoking-
related illness, even though I believe it would be laudable for my
physician to support anti-tobacco movements, I still need his
medical expertise right now in order to preserve my life. In con-
clusion, we emphasize that “care must be taken to assure that sub-
jective criteria about what the natural world should look like are not
confused with objective management goals” (Sinclair 1997).

References
Caughley, G. and A.R.E. Sinclair. 1994. Wildlife Ecology and Management.

Blackwell Scientific Publications, Boston, Massachusetts.

Holling, C.S. 1978. Adaptive Environmental Assessment and Management. J.
Wiley, London.

Micucci, P.A. and T. Waller. 2007. The management of Yellow Anacondas
(Eunectes notaeus) in Argentina: From historical misuse to resource appre-
ciation. Iguana 14: 160–171.

Micucci, P.A., T. Waller, and E. Alvarenga. 2006. Programa Curiyú. Para la con-
servación y aprovechamiento sustentable de la boa curiyú (Eunectes
notaeus) en la Argentina. Etapa experimental piloto 2002–2004,
Formosa, pp. 77–92. In: M.L. Bolkovic and D. Ramadori (eds.), Manejo
de Fauna Silvestre en la Argentina. Programas de Uso Sustentable. Dirección
de Fauna Silvestre, Secretaría de Ambiente y Desarrollo Sustentable,
Buenos Aires.

Rivas, J.A. 2007. Conservation of Green Anacondas: How Tylenol conserva-
tion and macroeconomics threaten the survival of the world’s largest
snake. Iguana 14: 74–85.

Sinclair, A.R.E. 1997. Carrying capacity and the overabundance of deer, pp.
380–394. In: W.J. McShea, H.B. Underwood, and J.H. Rappole (eds.),
The Science of Overabundance — Deer Ecology and Population
Management. Smithsonian Institution Press, Washington, DC.

Wallerstein, I. 1999. The End of the World As We Know It: Social Science for the
Twenty-first Century. University of Minnesota Press, Minneapolis.

Webb G. 2002. Conservation and sustainable use of wildlife: An evolving con-
cept. Pacific Conservation and Biology 8: 12–26.

Yellow Anaconda (Eunectes notaeus) skins (>230 cm) harvested between
2002 and 2007. Average: 3,800 (dotted line). *Definitive value pending.




