this is "nightline." >> tonight news from the showdown in nevada. it's the first contest in the west for the replican presidential hopefuls. and abc news is projecting that donald trump will finish first in the state's caucuses. can anything slow down his campaign? and we go into the wild to the front lines of a modern war to save an ancient animal from extinction. we're with the rangers riski their lives to track poex here's kill for the coveted rhino horns. >> the social media secrecy that led to their daughter's murder. in this world of anonymous prichtmessaging, so many parents have no idea what their kids are doing online. >> i wish i would have been

>> these students take us inside

first the night line five. >> good evening. breaking news as we come on the air. abc news can now project donald

nevada republican caucuses. based on our vote analysis, it is a two-person race for second between marco rubio and ted cr. a win for trump will make three victories in a row after took first prize in surlsouth carolina and new hampshire. people said they were in favor of the outsider and of those voters, 70% said they supported the billionaire businessman. we now turn to a high stakes war against trafficking. world more than gold, cocaine, even diamonds. the coveted horn of the rhino. but now a new military grade piece of machinery is being deployoyed in th fight againinst ruthless poachers. we go to the south african bush. >> in the pitch black of the south african bush, these rangers can only listen and smell for any sign that's the enemy is near.

will pick you up first. >> they hunt for rhino here every night. >> we need to protect them from being sh. >> tonight our patrol has eyes in the sky. we're on the front lines of a modern war. over an ancient animal. the future of the rhino is i in the balance. according to the world wildlife fun, in south africa alone, rhino poaching has skyrocketed 9,000% in just 8 years, fueled by a growing demand for its horn. ground up and used as a popular party drug in asia. more expensive than gold and some say more desirable than cocaine. with the millions made from the illegal trade, now ma nep-related and controlled by criminal networks, the plight of the rhino has gbal implications. in the oldest game reserve in south africa, they're trying something new.

a pilot project where unmanned aircraft are being deployedo help park rangers in their fight. >> nighttime operations has always been verery, very difficult for these guys. and besideseeting one the poachers you might be tracking, the danger to the animals. >> we'll just foul. you guys carry on. we'll just keep you in the frame. >> tonight's mission is about to begin and tensions are high. with ruthless poexers likely in the dark, and the reason news of a park worker mauled to death by a lion. don't let the laughter fool you. my nerves are kickingin.

other side of the bush. the drone infrared camera pks up heat signatures of animals and humans. and sendsds images back real-time the command centerer. the white dots are us on patrol. the experienced rangers keep several feet between them so if one of them is attacked, they don't a all go down at once. >> how many does it help? give you a sense of ease to some degree that you have this thing hovering above you now? >> i think it is quite fortunate with the drone above us. so the guys can see us. >> no signs of poachers dururing this patrol. but in this vast territory, the drones and patrols can only cover. so ground.

rhinos were killed. many of the rinl owes that survive these attacks are brought here to this nearby sanctuary. >> high, big fello. somebody messed you up. somebody got paid off you, big guy. >> like this mother and her calf. >> we hear poaching all the time look at this animal. first time i'm seeing it in my life up close and personal. but just, i mean, until you're thislose to it. that is brutal. >> three months ago rescuers found her in the bush, still groggy. her horn hacked off. left for dead. her baby clinging to her side. >> is the animal still in pain? >> no. >> as much as we can get a success. >> she is healing well and soon the two will be released back into the reserve. >> man oh man. it's a shame this place is even necessary.

think, what would drive someone to this kind of brutality, until you rlize a single rhino horn can fetch up to a quarter million dollars on n thelack market. even a small fraction of that is hard to resist in a place with little opportunity. >> we're in a township outside pretty pretoria. our poacher set up a meeting for us. >> a former poacher has agreed to meet us. only if we don't show his face. >> did you ever feel bad for what you were doi for killing these animals? >> throughgh translator he said he felt bad but needed money to feed his family. he became a shooter and he killed at least 50 rhinos. he said his crew always had a guy on the inside. a ranger on the take. >> park officials are being paid off.

the level of corruption stretches into local government offices. given the amounts of money, anyone is open to being corrupted. >> most of the money is taken by criminal networks. most of it ends upp here in vietnam. >> it is a status symbol for the rich. you grind it up in special designed dishes. mix it with rice wine and water. >> it is that said to cure everything. despite the ban on the trading of rhino horn, markets can still be found as seen in this bbc program. here the back of aailor shop. a deal is underway. >> how much are you charging? >> butt's a false promise. >> there is no scientific proof that rhino horn has any benefit.

is simy made of keratin. it is exactly the same as your finger nails. >> celebrities. >> ask your friends and family never to buy rhino ho. >> even prince william took up the cause. >> together we can save our wild rhinos. when the buying stops, the killing can too. >> these slick ads may only go so far. >> you're dealing with faith. people firmlmly believe that rhihino horn does have the a attribute that it is said to have. it is the same as telling a christian, jesus christ doesn't exist. that's the level of belief that you're dealing with. for many people, it crosses beyond that. >> in africa t focus is on steming the supply. to harvesting the horns and selling them legally. >> as you know, the rhino horn

it is a painless, relatively uninvasive procedure. >> i'm telling you, thihis is t way we will save the rhinos from extinction. >> while not everyone agrees on the best path forward, what we'vee seen here on the front lightnings are people trying everything. that's probably what it wilillo and more to win this battle against extinction. south africa. when we come back, the media. the digital dangers even the most tech savvy parents might not know a about.front of the school. that's where your friends are. seriously, it's, it really fine. you don't want to be seen with your dad? no, it's..no.. oh, there's tracy. at! [ horn honking ] [ forward collllision waing ] bye dad! it brakes when you don't. the newly redesigned volkswagen passat. right now you can get a $1,000 presidents' day bonus on new 2015 or 2016

red lobster's lobsterfest is back. so come try the largest variety of lobster dishes of the year, like lobster lover's dream or new dueling lobster tails. it's a party on every plate, and you're invited. so come in while it lasts. we stop arthritis pain, you don't have to stop. tylenol 8hr arthritis pain has two layers of pain relief. e first is fast. the second lasts all day. we give you your day back. what you do with it is up to you. tylenol . my son and i used to watch the red carpet shows on tv now, i'm walking them. life is unpredictable onone thing need to be predictable is to be flake free. because i have used head and shoulders for 20 years. used regularly, it removes up to 100% of flakes keeping u protected every week, every month, every year you ready ma? always life is unpredictable, so embrace i

here i in the ci, parking is hard to find. seems like e everyone ives. and those who do should switch to geico because you could save hundreds on car insurance. ah, perfect. valet parkin hello! here's the keys. and, uh, go easy on my ride, mate. hm, wouldn't mind some of that beef wellington... to see how much you could save on car surance, go to geico.com. ah! (car alarm sounds)

parenng has never been easy. it seal in the digital age, we have more blind spots to worry about. tonight, yahoo! global news anchor katie couric takes a look at a tragedy and gives as you glimpse at the world of teens and social mea. >> nicole was very lovable person. >> tammy weeks was facing the unimaginable. her 13-year-old daughter was found dead. >> she touched many people. >> a 13-year-old girl making headlines. >> the search for answers is just beginning. >> the reaction to her murder has become part of a conversation about girls and social media. nicole had secretly been messaging with this virginia tech student. 18-year-old david eisenhower. on the social media app kick. according to investigators, they

nicole snuck out of her parerents' house the meet up with eisenhower and never returned home. she was missing for three days until her body was discovered 80 miles away. >> a very preliminary determination of the cause of death is stabbing. >> nico's story has become a cautionary tale about the dangers of secret messaging apppps and their anonymous users. >> i'm willing to say kick is the devil for young children. it isike a free ability to text and parents can't see the number going in and out. >> eisenhower and an alleged female accomplice are now accused of kidnapping and murder of nicole. neither has entered a plea. nicole's father and step mother sat down with 2020. >> i wish you could have been there for my daughter. she deserved me to be there and i was not. >> nicole's family believes she turned to social media for acceptance after she was severely bullied in school. >> she had a huge boy crush kind

but it was kind of innocent. she was still a child. and all she wanted was just the attention. >> we reached out to the people who run kik and they told us, we have zero tolerance for any behavior that potentially affects safety of our users. we offer blocking and reporting tools to allow users to flag unwanted content. we are reviewing all aspects. >> whe this case surfaced, have you heard of kik? yes. from every girl that i interviewed. >> but those secret apps are just part of the story. nancy has been reporting on youth culture for more than a decade. in her new book, american girls, social media and the secret lives of teenagers. she explores the dangers of coming of age in a world ruled by social media. >> tell me about the role this is playing in the life of the avaverage teenage girl.

conversations i had with some girls in los angeles really set the tone for the whole book. she said social media is destroying our lives. i said so why don't you go off it? she said then i would have no life. >> she said what she discovevered was troubling. young lives playing out on various platforms that promote negative self-esteem. sometimes harsh judent and cyber bullying. sothing that 13-year-old carey has experienced. >> i got a message on instagram from this guy. he seems like he was my age so i thought could i trust him. he said that he knew some of my friends. i started talking too him and we got really close. >> the friendship took a turn and carey decided they should stop communicating. soon after, she said the boy and one of his friends began writing hurtful things. >> they were saying these things like you're ugly and cursing me out when they've never mete or know me at all.

>> her mom decided to do something about it. >> it had turned out thahat the person who was actually cyber bullying her was not the boy but a friend of his who he wa manipulating. and she had sort of taken on this crusade to get back at my daughter for no reason. i spoke to this woman. and i said your daughter is cyber bullying my child. d so she promised me it would never happen again. that she would talk to this kid's parents. an thankfully that did put an end to it. >> how has social media krebed to the notion of cyber bullying? almost every girl has been cyber bullied. they didn't necessarily call it that because it didn't lead to something. >> sale says social media has become a popularity contest. where teens seek validation from the pictures they post and the

she says it is having a major impact on how teenage girls view themselves. 18-year-old olivia agrees. >> i got over 150 likes. oh, you know, what a good picture i took. and then if you post a photo that you think is good as well and you don't get a the love likes, oh my god. should i take this down? >> she said she met some girls who spend hours taking pictures of themselves and manipulating the images. we asked olivia to show us how some of these a apps work. >> i can whiten my teeth. a w whiter smile. if i wanted to be s super blond. you cann make yourself look more slender. i can make my arm thinner. what some peopleon't realize is that, look at th door. it's not supposed to look like that.

these apps sparingly. >> sometimes if my voice gets really oily, i'll do that. but i don't reshape my body. >> how abt this depression we're hearing about among teenagers? >> think about it. if what you are thinking about is do i look hot? am i going to get liked on this photo? these the constant thoughts being raised in teenage girls' minds through their use of social media. it is not soothing. it is not something that produces a feeling of well being or security. >> both olivia and carey's moms say talking to their children about social media behavior is critically imimportant. >> basically, your tarnlg wants to know they are part of the conversation. >> this is the way the kids will communicate. this is way life is. and you need to have the channels of communication en. you need to educate them as

as to what the dangers are. >> for "nightline," katie couric in los angeles. nancy's book, american girls is on sale now. up next, a look ahead to a special event on "nightline" about a profoundlyly tic. consent on campus. lease a 2016 lincoln mkx for $399 a month

[woodworker] i i live inhe fine details. that's why i run on quickbooks. i use the payments app to accept credit cards... ...and everything autosyncs. those sales prove my sustainable designs are better for the environment and my bottoline. that's how i own it. your heart loves omega-3-3s. but the omega-3s in fish oil differ from megared krill oil. unlike fish oil, megared is easily absorbed by your body. megared.

sexual assault and the explosive mix of alcohol and

are some are calling fault lines. we hear from those whose allegations give us a lot to think about. >> if anyone had ever asked me, if someone has sex with you and you don't want them to have sex with you, will you stop them from doing that? thenswer would have 110% been yes. then when the situation actually arose, that was not my response to it. >> "nightline" invited experts and advocates to punish state university. some who see an epidemic of sexual violence. others who fee the pendulum has swung too far accusing men. we examine consent and whether it is a vital piece of sex education that's been missing. consent on castle.. a "nightline" event. thanks for watching abc news. overnight withreaking news and tune into "good morning america."

abc news.com. number one, kesha versus dr. luke, picking up steam and splitting music's biggest pop divas. >> they're free kesha.

dansnumber three, hillary's scandal. is mrs. clinton about to become a prime time gladiator? >> this is what they want to know. plus our "insider" bonus. snooki's torn up the jersey shore and nowshe's flipping it with her husband. if they d kill each other first. >> it's like you're annoying get away from me. >> and is apprentice boss arnold schwarzenegger better than the donald? >> it's the"the insider" together with yahoo! >> people versus o.j. simpson miniseries puts him back into the spotlight. we're goi to go into who was kardashian. let's get into our number